diff --git a/README.rst b/README.rst
index dbae11c..53c85d9 100644
--- a/README.rst
+++ b/README.rst
@@ -1,6 +1,12 @@
 OpenSoar
 ========
 
+busy with making everything timezone aware
+- wait on aerofiles fix for deepcopy
+- decide on dependencies. pinned or not?
+- run test with pysoar, same results?
+- how to keep backwards compatible? add flag?
+
 .. image:: https://img.shields.io/pypi/v/opensoar.svg
     :target: https://pypi.org/project/opensoar/
     :alt: pypi version and link
diff --git a/opensoar/competition/soaringspot.py b/opensoar/competition/soaringspot.py
index ff7acaa..97e52b4 100644
--- a/opensoar/competition/soaringspot.py
+++ b/opensoar/competition/soaringspot.py
@@ -17,8 +17,9 @@
 from opensoar.task.race_task import RaceTask
 from opensoar.task.task import Task
 from opensoar.task.waypoint import Waypoint
-from opensoar.utilities.helper_functions import dm2dd, subtract_times
+from opensoar.utilities.helper_functions import dm2dd
 from opensoar.competition.daily_results_page import DailyResultsPage
+from opensoar.utilities.helper_functions import double_iterator
 
 
 def get_comment_lines_from_parsed_file(parsed_igc_file: dict) -> List[str]:
@@ -46,7 +47,7 @@ def get_task_rules(lseeyou_tsk_line: str) -> Tuple[datetime.time, datetime.timed
     return start_opening, t_min, multi_start
 
 
-def get_info_from_comment_lines(parsed_igc_file: dict, start_time_buffer: int=0) -> Tuple[Optional[Task], dict, dict]:
+def get_info_from_comment_lines(parsed_igc_file: dict, date: datetime.date, start_time_buffer: int=0) -> Tuple[Optional[Task], dict, dict]:
     """
     There is specific contest information stored in the comment lines of the IGC files.
     This function extracts this information
@@ -84,8 +85,8 @@ def get_info_from_comment_lines(parsed_igc_file: dict, start_time_buffer: int=0)
             timezone = int(line.split(':')[3])
 
     if start_opening is not None:
-        # convert start opening to UTC time
-        start_opening = subtract_times(start_opening, datetime.timedelta(hours=timezone))
+        # make timezone aware datetime object
+        start_opening = datetime.datetime.combine(date=date, time=start_opening, tzinfo=datetime.timezone(datetime.timedelta(hours=timezone)))
 
     if len(lcu_lines) == 0 or len(lseeyou_lines) == 0:
         # somehow some IGC files do not contain the LCU or LSEEYOU lines with task information
@@ -345,10 +346,10 @@ def generate_competition_day(self, target_directory: str, download_progress=None
             try:
                 try:  # try utf-8
                     with open(file_path, 'r', encoding='utf-8') as f:
-                        parsed_igc_file = Reader().read(f)
+                        parsed_igc_file = Reader(skip_duplicates=True).read(f)
                 except UnicodeDecodeError:  # if not utf-8 use latin1
                     with open(file_path, 'r', encoding='latin1') as f:
-                        parsed_igc_file = Reader().read(f)
+                        parsed_igc_file = Reader(skip_duplicates=True).read(f)
             except Exception:
                 print('{} is skipped because the file could not be parsed'.format(competition_id))
                 continue
@@ -359,7 +360,7 @@ def generate_competition_day(self, target_directory: str, download_progress=None
                 continue
 
             # get info from file
-            task, contest_information, competitor_information = get_info_from_comment_lines(parsed_igc_file, start_time_buffer)
+            task, _, competitor_information = get_info_from_comment_lines(parsed_igc_file, date, start_time_buffer)
             plane_model = competitor_information.get('plane_model', None)
             pilot_name = competitor_information.get('pilot_name', None)
 
diff --git a/opensoar/task/aat.py b/opensoar/task/aat.py
index 12544e4..93b60c2 100644
--- a/opensoar/task/aat.py
+++ b/opensoar/task/aat.py
@@ -2,8 +2,7 @@
 from copy import deepcopy
 
 from opensoar.task.task import Task
-from opensoar.utilities.helper_functions import double_iterator, calculate_distance_bearing, calculate_destination, \
-    seconds_time_difference_fixes, add_times
+from opensoar.utilities.helper_functions import double_iterator, calculate_distance_bearing, calculate_destination
 
 
 class AAT(Task):
@@ -51,12 +50,12 @@ def apply_rules(self, trace):
         return fixes, start_time, outlanding_fix, distances, finish_time, sector_fixes
 
     def _determine_finish_time(self, fixes, outlanding_fix):
-        total_trip_time = seconds_time_difference_fixes(fixes[0], fixes[-1])
+        total_trip_time = (fixes[-1]['datetime'] - fixes[0]['datetime']).total_seconds()
         minimum_trip_time = self._t_min.total_seconds()
         if outlanding_fix is None and total_trip_time < minimum_trip_time:
-            finish_time = add_times(fixes[0]['time'], self._t_min)
+            finish_time = fixes[0]['datetime'] + self._t_min
         else:
-            finish_time = fixes[-1]['time']
+            finish_time = fixes[-1]['datetime']
         return finish_time
 
     def _calculate_trip_fixes(self, trace):
@@ -118,7 +117,7 @@ def _get_sector_fixes(self, trace):
                 if enl_first_fix is None:
                     enl_first_fix = fix
 
-                enl_time = seconds_time_difference_fixes(enl_first_fix, fix)
+                enl_time = (fix['datetime'] - enl_first_fix['datetime']).total_seconds()
                 if self.enl_time_exceeded(enl_time):
                     enl_registered = True
                     if current_leg > 0:
@@ -357,6 +356,7 @@ def _get_waypoint_fixes(self, outlanded, sector_fixes, outside_sector_fixes=None
         if outside_sector_fixes is None:
             outside_sector_fixes = list()
 
+        # this doesnt work due to latest aerofiles version
         waypoint_fixes = deepcopy(sector_fixes)
         if outlanded:
             waypoint_fixes.append(sector_fixes[-1])
diff --git a/opensoar/task/race_task.py b/opensoar/task/race_task.py
index 86e2b57..69a03fe 100644
--- a/opensoar/task/race_task.py
+++ b/opensoar/task/race_task.py
@@ -1,7 +1,7 @@
-from opensoar.task.task import Task
-from opensoar.utilities.helper_functions import calculate_distance_bearing, double_iterator, \
-    seconds_time_difference_fixes, add_seconds
+import datetime
 
+from opensoar.task.task import Task
+from opensoar.utilities.helper_functions import calculate_distance_bearing, double_iterator
 
 class RaceTask(Task):
     """
@@ -82,7 +82,7 @@ def apply_rules(self, trace):
         fixes, outlanding_fix = self.determine_trip_fixes(trace)
         distances = self.determine_trip_distances(fixes, outlanding_fix)
         refined_start = self.determine_refined_start(trace, fixes)
-        finish_time = fixes[-1]['time']
+        finish_time = fixes[-1]['datetime']
         sector_fixes = []  # not applicable for race tasks
         return fixes, refined_start, outlanding_fix, distances, finish_time, sector_fixes
 
@@ -100,7 +100,7 @@ def determine_trip_fixes(self, trace):
                 if enl_first_fix is None:
                     enl_first_fix = fix_minus1
 
-                enl_time = seconds_time_difference_fixes(enl_first_fix, fix)
+                enl_time = (fix['datetime'] - enl_first_fix['datetime']).total_seconds()
                 enl_registered = enl_registered or self.enl_time_exceeded(enl_time)
             elif not enl_registered:
                 enl_first_fix = None
@@ -108,7 +108,7 @@ def determine_trip_fixes(self, trace):
             if self.start_opening is None:
                 after_start_opening = True
             else:
-                after_start_opening = add_seconds(fix['time'], self.start_time_buffer) > self.start_opening
+                after_start_opening = self.start_opening + datetime.timedelta(seconds=self.start_time_buffer) < fix['datetime']
 
             if leg == -1 and after_start_opening:
                 if self.started(fix_minus1, fix):
diff --git a/opensoar/task/task.py b/opensoar/task/task.py
index 78f8ff1..8632939 100644
--- a/opensoar/task/task.py
+++ b/opensoar/task/task.py
@@ -14,8 +14,8 @@ class Task:
     ENL_VALUE_THRESHOLD = 500
     ENL_TIME_THRESHOLD = 30
 
-    def __init__(self, waypoints: List[Waypoint], timezone: int, start_opening: datetime.time, start_time_buffer: int,
-                 multistart: bool):
+    def __init__(self, waypoints: List[Waypoint], timezone: int, start_opening: datetime.datetime,
+                 start_time_buffer: int, multistart: bool):
         """
         :param waypoints:
         :param timezone: time difference wrt UTC in hours
@@ -150,7 +150,7 @@ def determine_refined_start(self, trace, fixes):
 
         for fix, next_fix in double_iterator(interpolated_fixes):
             if self.started(fix, next_fix):
-                return fix['time']
+                return fix['datetime']
 
         raise ValueError('Start should have been determined')
 
diff --git a/opensoar/task/trip.py b/opensoar/task/trip.py
index 493214c..ec9c933 100644
--- a/opensoar/task/trip.py
+++ b/opensoar/task/trip.py
@@ -1,6 +1,3 @@
-from opensoar.utilities.helper_functions import seconds_time_difference
-
-
 class Trip:
     """
     Realised
@@ -47,11 +44,11 @@ def fix_on_leg(self, fix, leg):
         return larger_than_minimum and smaller_than_maximum
 
     def fix_before_leg(self, fix, leg):
-        return seconds_time_difference(fix['time'], self.fixes[leg]['time']) >= 0
+        return (self.fixes[leg]['datetime'] - fix['datetime']).total_seconds() >= 0
 
     def fix_after_leg(self, fix, leg):
         if leg + 1 <= self.completed_legs():
-            return seconds_time_difference(self.fixes[leg + 1]['time'], fix['time']) >= 0
+            return (fix['datetime'] - self.fixes[leg + 1]['datetime']).total_seconds() >= 0
         elif self.outlanded() and leg == self.outlanding_leg():
             return False
         else:  # leg > self.completed_legs() + 1
diff --git a/opensoar/thermals/pysoar_thermal_detector.py b/opensoar/thermals/pysoar_thermal_detector.py
index 120d38f..693e51d 100644
--- a/opensoar/thermals/pysoar_thermal_detector.py
+++ b/opensoar/thermals/pysoar_thermal_detector.py
@@ -1,5 +1,4 @@
-from opensoar.utilities.helper_functions import triple_iterator, calculate_bearing_change, calculate_distance_bearing, \
-    seconds_time_difference
+from opensoar.utilities.helper_functions import triple_iterator, calculate_bearing_change, calculate_distance_bearing
 
 
 class PySoarThermalDetector:
@@ -34,13 +33,13 @@ def analyse(self, trace):
 
         for fix_minus2, fix_minus1, fix in triple_iterator(trace):
 
-            time_minus2 = fix_minus2['time']
-            time_minus1 = fix_minus1['time']
-            time = fix['time']
+            time_minus2 = fix_minus2['datetime']
+            time_minus1 = fix_minus1['datetime']
+            time = fix['datetime']
 
             bearing_change = calculate_bearing_change(fix_minus2, fix_minus1, fix)
-            delta_t = (0.5 * seconds_time_difference(time_minus1, time) +
-                       0.5 * seconds_time_difference(time_minus2, time))
+            delta_t = (0.5 * (time - time_minus1).total_seconds() +
+                       0.5 * (time - time_minus2).total_seconds())
             bearing_change_rate = bearing_change / delta_t
 
             if cruise:
@@ -101,7 +100,7 @@ def analyse(self, trace):
                         possible_cruise_fixes.append(fix)
                         total_bearing_change += bearing_change
 
-                    delta_t = seconds_time_difference(possible_cruise_fixes[0]['time'], time)
+                    delta_t = (time - possible_cruise_fixes[0]['datetime']).total_seconds()
                     cruise_distance, _ = calculate_distance_bearing(possible_cruise_fixes[0], fix)
                     temp_bearing_rate_avg = 0 if delta_t == 0 else total_bearing_change / delta_t
 
diff --git a/opensoar/utilities/helper_functions.py b/opensoar/utilities/helper_functions.py
index 746c487..4941a06 100644
--- a/opensoar/utilities/helper_functions.py
+++ b/opensoar/utilities/helper_functions.py
@@ -124,10 +124,6 @@ def altitude_gain_and_loss(fixes: List[dict], gps_altitude=True):
     return gain, loss
 
 
-def seconds_time_difference_fixes(fix1, fix2):
-    return seconds_time_difference(fix1['time'], fix2['time'])
-
-
 def total_distance_travelled(fixes: List[dict]):
     """Calculates the total distance, summing over the inter fix distances"""
     distance = 0
@@ -138,61 +134,6 @@ def total_distance_travelled(fixes: List[dict]):
     return distance
 
 
-def seconds_time_difference(time1: datetime.time, time2: datetime.time):
-    """
-    Determines the time difference between to datetime.time instances, mocking the operation time2 - time1
-    It is assumed that both take place at the same day.
-    :param time1: 
-    :param time2: 
-    :return: time difference in seconds
-    """
-
-    today = datetime.date.today()
-    time_diff = datetime.datetime.combine(today, time2) - datetime.datetime.combine(today, time1)
-    return time_diff.total_seconds()
-
-
-def add_times(start_time: datetime.time, delta_time: datetime.timedelta):
-    """
-    Helper to circumvent problem that normal datetime.time instances can not be added.
-    :param start_time:
-    :param delta_time:
-    :return:
-    """
-    full_datetime_start = datetime.datetime.combine(datetime.date.today(), start_time)
-
-    full_datetime_result = full_datetime_start + delta_time
-    return full_datetime_result.time()
-
-
-def subtract_times(start_time: datetime.time, delta_time: datetime.timedelta):
-    full_datetime_start = datetime.datetime.combine(datetime.date.today(), start_time)
-    full_datetime_result = full_datetime_start - delta_time
-    return full_datetime_result.time()
-
-
-def add_seconds(time: datetime.time, seconds: int) -> datetime.time:
-    """
-    Add seconds to datetime.time object and return resulting datetime.time object.
-
-    :param time:
-    :param seconds: not limited to 0-59.
-    :return:
-    """
-
-    additional_seconds = seconds
-
-    additional_hours = additional_seconds // 3600
-    additional_seconds -= additional_hours * 3600
-
-    additional_minutes = additional_seconds // 60
-    additional_seconds -= additional_minutes * 60
-
-    return add_times(time, datetime.timedelta(hours=additional_hours,
-                                              minutes=additional_minutes,
-                                              seconds=additional_seconds))
-
-
 def range_with_bounds(start: int, stop: int, interval: int) -> List[int]:
     """Return list"""
     result = [int(val) for val in range(start, stop, interval)]
@@ -202,8 +143,7 @@ def range_with_bounds(start: int, stop: int, interval: int) -> List[int]:
 
 
 def calculate_time_differences(time1, time2, interval):
-    total_difference = int(seconds_time_difference(time1, time2))
-    differences = range_with_bounds(0, total_difference, interval)
+    differences = range_with_bounds(0, int((time2 - time1).total_seconds()), interval)
     return differences
 
 
@@ -217,7 +157,7 @@ def interpolate_fixes(fix1, fix2, interval=1):
     :return: list of fixes between fix1 and fix2 with given interval
     """
 
-    time_differences = calculate_time_differences(fix1['time'], fix2['time'], interval)
+    time_differences = calculate_time_differences(fix1['datetime'], fix2['datetime'], interval)
 
     fixes = list()
     for difference in time_differences:
@@ -225,9 +165,8 @@ def interpolate_fixes(fix1, fix2, interval=1):
 
         lat = fix1['lat'] + fraction * (fix2['lat'] - fix1['lat'])
         lon = fix1['lon'] + fraction * (fix2['lon'] - fix1['lon'])
-        time = add_seconds(fix1['time'], difference)
-
-        fixes.append(dict(time=time, lat=lat, lon=lon))
+        time = fix1['datetime'] + datetime.timedelta(seconds=difference)
+        fixes.append(dict(datetime=time, lat=lat, lon=lon))
 
     return fixes
 
diff --git a/requirements.txt b/requirements.txt
index 2104fd4..9e9810d 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,5 +1,5 @@
 pyproj
-aerofiles
-beautifulsoup4
-geojson
-shapely
+aerofiles==1.4.0
+beautifulsoup4==4.12.3
+geojson==3.1.0
+shapely==2.0.6
diff --git a/tests/competition/test_soaringspot.py b/tests/competition/test_soaringspot.py
index a809cd7..569ccfc 100644
--- a/tests/competition/test_soaringspot.py
+++ b/tests/competition/test_soaringspot.py
@@ -194,5 +194,5 @@ def test_get_info_from_comment_lines_no_lcu_no_lseeyou(self):
         with open(igc_path, 'r', encoding='latin1') as f:
             parsed_igc_file = Reader().read(f)
 
-        task, contest_information, competitor_information = get_info_from_comment_lines(parsed_igc_file)
+        task, contest_information, competitor_information = get_info_from_comment_lines(parsed_igc_file, date=datetime.date(2023, 7, 4))
         self.assertIsNone(task, None)
diff --git a/tests/competition/test_strepla.py b/tests/competition/test_strepla.py
index e9db984..5d09c47 100644
--- a/tests/competition/test_strepla.py
+++ b/tests/competition/test_strepla.py
@@ -9,7 +9,6 @@
 from opensoar.competition.competitor import Competitor
 from opensoar.competition.strepla import get_waypoint_name_lat_long, get_waypoints, get_waypoint, get_task_and_competitor_info, get_info_from_comment_lines
 from opensoar.task.aat import AAT
-from opensoar.utilities.helper_functions import seconds_time_difference
 
 
 class TestStrepla(unittest.TestCase):
@@ -107,8 +106,11 @@ def test_aat_from_file(self):
         competitor = Competitor(trace, 'CX', 'Discus2b', 1, 'Karsten Leucker')
         competitor.analyse(task, 'pysoar')
 
-        time_diff = seconds_time_difference(competitor.trip.refined_start_time, datetime.time(13, 22, 40))
+        self.assertEqual(competitor.trip.refined_start_time.hour, 13)
+        self.assertEqual(competitor.trip.refined_start_time.minute, 22)
+        seconds = competitor.trip.refined_start_time.second
+
         dist_diff = sum(competitor.trip.distances) - 283500
-        self.assertLessEqual(abs(time_diff), 1)
+        self.assertLessEqual(abs(seconds-40), 1)
         self.assertEqual(len(competitor.trip.fixes), len(expected_waypoints))
         self.assertLessEqual(abs(dist_diff), 1000)
diff --git a/tests/task/helper_functions.py b/tests/task/helper_functions.py
index 66afb46..7d2bc5d 100644
--- a/tests/task/helper_functions.py
+++ b/tests/task/helper_functions.py
@@ -5,7 +5,7 @@
 
 def get_trace(igc_path):
     with open(igc_path, 'r') as f:
-        parsed_igc_file = Reader().read(f)
+        parsed_igc_file = Reader(skip_duplicates=True).read(f)
 
     _, trace = parsed_igc_file['fix_records']
 
@@ -14,7 +14,7 @@ def get_trace(igc_path):
 
 def get_task(igc_path):
     with open(igc_path, 'r') as f:
-        parsed_igc_file = Reader().read(f)
+        parsed_igc_file = Reader(skip_duplicates=True).read(f)
 
-    task, contest_information, competitor_information = get_info_from_comment_lines(parsed_igc_file)
+    task, contest_information, competitor_information = get_info_from_comment_lines(parsed_igc_file, date=parsed_igc_file["header"][1]["utc_date"])
     return task
diff --git a/tests/task/test_aat_trip.py b/tests/task/test_aat_trip.py
index 7ac4113..963e2bc 100644
--- a/tests/task/test_aat_trip.py
+++ b/tests/task/test_aat_trip.py
@@ -23,13 +23,13 @@ def test_total_distance(self):
         self.assertAlmostEqual(total_distance / 1e3, 199.42, places=2)
 
     def test_start_time(self):
-        start_time = self.trip.fixes[0]['time']
-        expected_start_time = datetime.time(12, 22, 8)
+        start_time = self.trip.fixes[0]['datetime']
+        expected_start_time = datetime.datetime(2012, 5, 26, 12, 22, 8, tzinfo=datetime.timezone.utc)
         self.assertEqual(expected_start_time, start_time)
 
     def test_finish_time(self):
         finish_time = self.trip.finish_time
-        expected_finish_time = datetime.time(15, 52, 8)
+        expected_finish_time = datetime.datetime(2012, 5, 26, 15, 52, 8, tzinfo=datetime.timezone.utc)
         self.assertEqual(expected_finish_time, finish_time)
 
 
@@ -54,10 +54,10 @@ def test_trip_fixes(self):
         # assert if opensoar finds same fixes as seeyou, based on time
         fix_times = [
             # tuple with (opensoar time, SeeYou time)
-            (self.trip.refined_start_time, datetime.time(12, 14, 21)),
-            (self.trip.fixes[1]['time'], datetime.time(12, 49, 22)),
-            (self.trip.fixes[2]['time'], datetime.time(13, 26, 14)),
-            (self.trip.outlanding_fix['time'], datetime.time(14, 8, 0)),
+            (self.trip.refined_start_time, datetime.datetime(2012, 5, 26, 12, 14, 21, tzinfo=datetime.timezone.utc)),
+            (self.trip.fixes[1]['datetime'], datetime.datetime(2012, 5, 26, 12, 49, 22, tzinfo=datetime.timezone.utc)),
+            (self.trip.fixes[2]['datetime'], datetime.datetime(2012, 5, 26, 13, 26, 14, tzinfo=datetime.timezone.utc)),
+            (self.trip.outlanding_fix['datetime'], datetime.datetime(2012, 5, 26, 14, 8, 0, tzinfo=datetime.timezone.utc)),
         ]
 
         for opensoar_time, seeyou_time in fix_times:
@@ -90,11 +90,11 @@ def test_trip_fixes(self):
         # assert if opensoar finds same fixes as seeyou, based on time
         fix_times = [
             # tuple with (opensoar time, SeeYou time)
-            (self.trip.refined_start_time, datetime.time(12, 24, 14)),
-            (self.trip.fixes[1]['time'], datetime.time(12, 57, 53)),
-            (self.trip.fixes[2]['time'], datetime.time(13, 42, 31)),
-            (self.trip.fixes[3]['time'], datetime.time(14, 4, 5)),
-            (self.trip.outlanding_fix['time'], datetime.time(14, 5, 49)),
+            (self.trip.refined_start_time, datetime.datetime(2012, 5, 26, 12, 24, 14, tzinfo=datetime.timezone.utc)),
+            (self.trip.fixes[1]['datetime'], datetime.datetime(2012, 5, 26, 12, 57, 53, tzinfo=datetime.timezone.utc)),
+            (self.trip.fixes[2]['datetime'], datetime.datetime(2012, 5, 26, 13, 42, 31, tzinfo=datetime.timezone.utc)),
+            (self.trip.fixes[3]['datetime'], datetime.datetime(2012, 5, 26, 14, 4, 5, tzinfo=datetime.timezone.utc)),
+            (self.trip.outlanding_fix['datetime'], datetime.datetime(2012, 5, 26, 14, 5, 49, tzinfo=datetime.timezone.utc)),
         ]
 
         for opensoar_time, seeyou_time in fix_times:
diff --git a/tests/task/test_trip.py b/tests/task/test_trip.py
index c792ba0..f6467ae 100644
--- a/tests/task/test_trip.py
+++ b/tests/task/test_trip.py
@@ -31,13 +31,12 @@ def test_outlanded(self):
     def test_start_time(self):
         start_fix = self.trip.fixes[0]
         refined_start_time = self.trip.refined_start_time
-        self.assertEqual(start_fix['time'], datetime.time(12, 12, 54))
-        self.assertEqual(refined_start_time, datetime.time(12, 12, 55))
+        self.assertEqual(start_fix['datetime'], datetime.datetime(2014, 6, 21, 12, 12, 54, tzinfo=datetime.timezone.utc))
+        self.assertEqual(refined_start_time, datetime.datetime(2014, 6, 21, 12, 12, 55, tzinfo=datetime.timezone.utc))
 
     def test_finish_time(self):
         finish_fix = self.trip.fixes[-1]
-        self.assertEqual(finish_fix['time'], datetime.time(13, 21, 58))
-
+        self.assertEqual(finish_fix['datetime'], datetime.datetime(2014, 6, 21, 13, 21, 58, tzinfo=datetime.timezone.utc))
 
 class TestOutlandingTrip(unittest.TestCase):
     """
@@ -59,7 +58,7 @@ def test_completed_legs(self):
 
     def test_fix_after_leg_on_outlanding_leg(self):
         """A fix happening on the outlanding leg can never be after the leg, because that leg is never finished."""
-        fix = {'time': datetime.time(14, 44, 45)}
+        fix = {'datetime': datetime.datetime(2014, 6, 21, 14, 44, 45)}
         fix_after_leg = self.trip.fix_after_leg(fix, leg=2)
         self.assertFalse(fix_after_leg)
 
diff --git a/tests/thermals/test_flight_phases.py b/tests/thermals/test_flight_phases.py
index dc82760..c68cfa0 100644
--- a/tests/thermals/test_flight_phases.py
+++ b/tests/thermals/test_flight_phases.py
@@ -5,7 +5,7 @@
 
 from opensoar.task.trip import Trip
 from opensoar.thermals.flight_phases import FlightPhases
-from opensoar.utilities.helper_functions import double_iterator, seconds_time_difference
+from opensoar.utilities.helper_functions import double_iterator
 
 from tests.task.helper_functions import get_trace, get_task
 
@@ -13,17 +13,17 @@
 class TestFlightPhases(unittest.TestCase):
 
     pysoar_phase_start_times = [
-        datetime.time(12, 12, 52),
-        datetime.time(12, 20, 22),
-        datetime.time(12, 24, 14),
-        datetime.time(12, 29, 22),
-        datetime.time(12, 33, 6),
-        datetime.time(12, 34, 50),
-        datetime.time(12, 37, 42),
-        datetime.time(12, 47, 14),
-        datetime.time(12, 52, 42),
-        datetime.time(13, 1, 0),
-        datetime.time(13, 4, 52),
+        datetime.datetime(2014, 6, 21, 12, 12, 52, tzinfo=datetime.timezone.utc),
+        datetime.datetime(2014, 6, 21, 12, 20, 22, tzinfo=datetime.timezone.utc),
+        datetime.datetime(2014, 6, 21, 12, 24, 14, tzinfo=datetime.timezone.utc),
+        datetime.datetime(2014, 6, 21, 12, 29, 22, tzinfo=datetime.timezone.utc),
+        datetime.datetime(2014, 6, 21, 12, 33, 6, tzinfo=datetime.timezone.utc),
+        datetime.datetime(2014, 6, 21, 12, 34, 50, tzinfo=datetime.timezone.utc),
+        datetime.datetime(2014, 6, 21, 12, 37, 42, tzinfo=datetime.timezone.utc),
+        datetime.datetime(2014, 6, 21, 12, 47, 14, tzinfo=datetime.timezone.utc),
+        datetime.datetime(2014, 6, 21, 12, 52, 42, tzinfo=datetime.timezone.utc),
+        datetime.datetime(2014, 6, 21, 13, 1, 0, tzinfo=datetime.timezone.utc),
+        datetime.datetime(2014, 6, 21, 13, 4, 52, tzinfo=datetime.timezone.utc),
     ]
 
     cwd = os.path.dirname(__file__)
@@ -47,7 +47,7 @@ def test_all_phases(self):
 
         # check if start times of phases are within 2 seconds
         for phase, pysoar_phase_start_time in zip(all_phases, self.pysoar_phase_start_times):
-            time_diff = seconds_time_difference(phase.fixes[0]['time'], pysoar_phase_start_time)
+            time_diff = (pysoar_phase_start_time - phase.fixes[0]['datetime']).total_seconds()
             self.assertLessEqual(abs(time_diff), 2)
 
     def test_thermals(self):
@@ -60,7 +60,7 @@ def test_thermals(self):
 
         # check if correct phases are classified as thermals
         for thermal, pysoar_start_time in zip(thermals, self.pysoar_phase_start_times[1::2]):
-            time_diff = seconds_time_difference(thermal.fixes[0]['time'], pysoar_start_time)
+            time_diff = (pysoar_start_time - thermal.fixes[0]['datetime']).total_seconds()
             self.assertLessEqual(abs(time_diff), 2)
 
     def test_cruises(self):
@@ -73,7 +73,7 @@ def test_cruises(self):
 
         # check if correct phases are classified as cruises
         for cruise, pysoar_start_time in zip(cruises, self.pysoar_phase_start_times[0::2]):
-            time_diff = seconds_time_difference(cruise.fixes[0]['time'], pysoar_start_time)
+            time_diff = (pysoar_start_time - cruise.fixes[0]['datetime']).total_seconds()
             self.assertLessEqual(abs(time_diff), 2)
 
     def test_thermals_on_leg(self):
@@ -87,16 +87,18 @@ def test_thermals_on_leg(self):
         for thermal in thermals_leg2:
             self.assertFalse(thermal.is_cruise)
 
-        leg_start_time = self.trip.fixes[1]['time']
-        leg_end_time = self.trip.fixes[2]['time']
+        leg_start_time = self.trip.fixes[1]['datetime']
+        leg_end_time = self.trip.fixes[2]['datetime']
 
-        # check starttime of first thermal
-        start_time = thermals_leg2[0].fixes[0]['time']
-        self.assertEqual(seconds_time_difference(start_time, leg_start_time), 0)
+        # check start-time of first thermal
+        start_time = thermals_leg2[0].fixes[0]['datetime']
+        diff = (leg_start_time - start_time).total_seconds()
+        self.assertEqual(diff, 0)
 
         # check endtime of last thermal
-        end_time = thermals_leg2[-1].fixes[-1]['time']
-        self.assertEqual(seconds_time_difference(end_time, leg_end_time), 0)
+        end_time = thermals_leg2[-1].fixes[-1]['datetime']
+        diff = (leg_end_time - end_time).total_seconds()
+        self.assertEqual(diff, 0)
 
     def test_cruises_on_leg(self):
 
@@ -114,21 +116,26 @@ def test_phases_on_leg_spanning_complete_leg(self):
         the end of the leg."""
 
         trace = [
-            {'time': datetime.time(11, 33, 26), 'lat': 52.468183333333336, 'lon': 6.3402, 'validity': 'A',
+            {'datetime': datetime.datetime(2012, 5, 26, 11, 33, 26, tzinfo=datetime.timezone.utc), 'lat': 52.468183333333336, 'lon': 6.3402, 'validity': 'A',
              'pressure_alt': -37, 'gps_alt': 47, 'FXA': 2, 'SIU': 1},
-            {'time': datetime.time(11, 33, 34), 'lat': 52.468183333333336, 'lon': 6.3402, 'validity': 'A',
+            {'datetime': datetime.datetime(2012, 5, 26, 11, 33, 34, tzinfo=datetime.timezone.utc), 'lat': 52.468183333333336, 'lon': 6.3402, 'validity': 'A',
              'pressure_alt': -37, 'gps_alt': 47, 'FXA': 2, 'SIU': 1},
-            {'time': datetime.time(11, 33, 42), 'lat': 52.468183333333336, 'lon': 6.3402, 'validity': 'A',
+            {'datetime': datetime.datetime(2012, 5, 26, 11, 33, 42, tzinfo=datetime.timezone.utc), 'lat': 52.468183333333336, 'lon': 6.3402, 'validity': 'A',
              'pressure_alt': -37, 'gps_alt': 47, 'FXA': 2, 'SIU': 1},
-            {'time': datetime.time(11, 33, 50), 'lat': 52.468183333333336, 'lon': 6.3402, 'validity': 'A',
+            {'datetime': datetime.datetime(2012, 5, 26, 11, 33, 50, tzinfo=datetime.timezone.utc), 'lat': 52.468183333333336, 'lon': 6.3402, 'validity': 'A',
              'pressure_alt': -37, 'gps_alt': 48, 'FXA': 1, 'SIU': 1},
-            {'time': datetime.time(11, 33, 58), 'lat': 52.468183333333336, 'lon': 6.340216666666667, 'validity': 'A',
+            {'datetime': datetime.datetime(2012, 5, 26, 11, 33, 58, tzinfo=datetime.timezone.utc), 'lat': 52.468183333333336, 'lon': 6.340216666666667, 'validity': 'A',
              'pressure_alt': -37, 'gps_alt': 48, 'FXA': 1, 'SIU': 1},
-            {'time': datetime.time(11, 34, 6), 'lat': 52.46816666666667, 'lon': 6.339666666666667, 'validity': 'A',
+            {'datetime': datetime.datetime(2012, 5, 26, 11, 34, 6, tzinfo=datetime.timezone.utc), 'lat': 52.46816666666667, 'lon': 6.339666666666667, 'validity': 'A',
              'pressure_alt': -38, 'gps_alt': 49, 'FXA': 1, 'SIU': 1},
         ]
 
-        trip = deepcopy(self.trip)
+        # originally this did trip = deepcopy(self._trip)
+        # but this is broken with current aerofiles version
+        _trace = get_trace(self.igc_path)
+        race_task = get_task(self.igc_path)
+        trip = Trip(race_task, _trace)
+
         trip.fixes = [
             trace[1],
             trace[4]
@@ -139,8 +146,8 @@ def test_phases_on_leg_spanning_complete_leg(self):
         # there should only be one phase: starting at first fix and ending at last fix of trace
         # these are conditions to a correct test setup, therefore no actual tests
         assert len(phases._phases) == 1
-        assert phases._phases[0].fixes[0]['time'] == trace[0]['time']
-        assert phases._phases[0].fixes[-1]['time'] == trace[-1]['time']
+        assert phases._phases[0].fixes[0]['datetime'] == trace[0]['datetime']
+        assert phases._phases[0].fixes[-1]['datetime'] == trace[-1]['datetime']
 
         all_phases_leg0 = phases.all_phases(leg=0)
 
@@ -150,5 +157,5 @@ def test_phases_on_leg_spanning_complete_leg(self):
         # check if phase correctly starts and ends at the trip fixes and not the trace fixes
         first_phase_fix = all_phases_leg0[0].fixes[0]
         last_phase_fix = all_phases_leg0[0].fixes[-1]
-        self.assertEqual(first_phase_fix['time'], trip.fixes[0]['time'])
-        self.assertEqual(last_phase_fix['time'], trip.fixes[-1]['time'])
+        self.assertEqual(first_phase_fix['datetime'], trip.fixes[0]['datetime'])
+        self.assertEqual(last_phase_fix['datetime'], trip.fixes[-1]['datetime'])
diff --git a/tests/utilities/test_helper_functions.py b/tests/utilities/test_helper_functions.py
index 616d37a..730d554 100644
--- a/tests/utilities/test_helper_functions.py
+++ b/tests/utilities/test_helper_functions.py
@@ -2,12 +2,11 @@
 
 import datetime
 
-from opensoar.utilities.helper_functions import seconds_time_difference, interpolate_fixes, dm2dd, dms2dd, \
-    both_none_or_same_float, both_none_or_same_str, add_times, subtract_times
+from opensoar.utilities.helper_functions import interpolate_fixes, dm2dd, dms2dd, \
+    both_none_or_same_float, both_none_or_same_str
 from opensoar.utilities.helper_functions import double_iterator
 from opensoar.utilities.helper_functions import triple_iterator
 from opensoar.utilities.helper_functions import calculate_distance_bearing
-from opensoar.utilities.helper_functions import add_seconds
 from opensoar.utilities.helper_functions import range_with_bounds
 from opensoar.utilities.helper_functions import calculate_time_differences
 
@@ -31,43 +30,6 @@ def test_calculate_distance_equal_fixes(self):
 
         self.assertEqual(calculate_distance_bearing(fix1, fix2)[0], 0)
 
-    def test_seconds_time_difference(self):
-
-        time1 = datetime.time(0, 0, 10)
-        time2 = datetime.time(0, 0, 15)
-
-        result = seconds_time_difference(time1, time2)
-        expected_result = 5
-
-        self.assertEqual(result, expected_result)
-
-    def test_add_seconds(self):
-
-        time1 = datetime.time(12, 0, 0)
-        time2 = datetime.time(12, 0, 55)
-
-        self.assertEqual(add_seconds(time1, 20), datetime.time(12, 0, 20))
-        self.assertEqual(add_seconds(time2, 20), datetime.time(12, 1, 15))
-        self.assertEqual(add_seconds(time1, 3665), datetime.time(13, 1, 5))
-
-    def test_add_times(self):
-        time1 = datetime.time(12, 0, 0)
-        time2 = datetime.timedelta(hours=1, minutes=10, seconds=20)
-
-        result = add_times(time1, time2)
-        expected_result = datetime.time(13, 10, 20)
-
-        self.assertEqual(result, expected_result)
-
-    def test_subtract_times(self):
-        time1 = datetime.time(12, 20, 10)
-        time2 = datetime.timedelta(hours=1, minutes=10, seconds=5)
-
-        result = subtract_times(time1, time2)
-        expected_result = datetime.time(11, 10, 5)
-
-        self.assertEqual(result, expected_result)
-
     def test_range_with_bounds(self):
         self.assertListEqual(range_with_bounds(start=2, stop=4, interval=2), [2, 4])
         self.assertListEqual(range_with_bounds(start=2, stop=6, interval=2), [2, 4, 6])
@@ -76,16 +38,16 @@ def test_range_with_bounds(self):
 
     def test_calculate_time_differences(self):
 
-        time1 = datetime.time(12, 0, 50)
-        time2 = datetime.time(12, 0, 55)
-        time3 = datetime.time(12, 1, 2)
+        time1 = datetime.datetime(2012, 5, 26, 12, 0, 50, tzinfo=datetime.timezone.utc)
+        time2 = datetime.datetime(2012, 5, 26, 12, 0, 55, tzinfo=datetime.timezone.utc)
+        time3 = datetime.datetime(2012, 5, 26, 12, 1, 2, tzinfo=datetime.timezone.utc)
 
         self.assertListEqual(calculate_time_differences(time1, time2, 2), [0, 2, 4, 5])
         self.assertListEqual(calculate_time_differences(time2, time3, 2), [0, 2, 4, 6, 7])
 
     def test_interpolate_fixes(self):
-        fix1 = dict(time=datetime.time(12, 0, 10), lat=50, lon=6)
-        fix2 = dict(time=datetime.time(12, 0, 14), lat=58, lon=8)
+        fix1 = dict(datetime=datetime.datetime(2012, 5, 26, 12, 0, 10, tzinfo=datetime.timezone.utc), lat=50, lon=6)
+        fix2 = dict(datetime=datetime.datetime(2012, 5, 26, 12, 0, 14, tzinfo=datetime.timezone.utc), lat=58, lon=8)
 
         interpolated_fixes = interpolate_fixes(fix1, fix2)
 
@@ -93,18 +55,18 @@ def test_interpolate_fixes(self):
         self.assertEqual(len(interpolated_fixes), 5)
 
         times = [
-            datetime.time(12, 0, 10),
-            datetime.time(12, 0, 11),
-            datetime.time(12, 0, 12),
-            datetime.time(12, 0, 13),
-            datetime.time(12, 0, 14)
+            datetime.datetime(2012, 5, 26, 12, 0, 10, tzinfo=datetime.timezone.utc),
+            datetime.datetime(2012, 5, 26, 12, 0, 11, tzinfo=datetime.timezone.utc),
+            datetime.datetime(2012, 5, 26, 12, 0, 12, tzinfo=datetime.timezone.utc),
+            datetime.datetime(2012, 5, 26, 12, 0, 13, tzinfo=datetime.timezone.utc),
+            datetime.datetime(2012, 5, 26, 12, 0, 14, tzinfo=datetime.timezone.utc)
         ]
         lats = [50, 52, 54, 56, 58]
         lons = [6, 6.5, 7.0, 7.5, 8.0]
 
         # check individual entries
         for time, lat, lon, interpolated_fix in zip(times, lats, lons, interpolated_fixes):
-            self.assertEqual(interpolated_fix['time'], time)
+            self.assertEqual(interpolated_fix['datetime'], time)
             self.assertEqual(interpolated_fix['lat'], lat)
             self.assertEqual(interpolated_fix['lon'], lon)