Fix error in days to microseconds calculation

src/fable-library-py/fable_library/date.py

@@ -19,7 +19,7 @@ def subtract(x: datetime, y: datetime | TimeSpan) -> datetime | TimeSpan:
         delta = x - y
         # ts.microseconds only contains the microseconds provided to the constructor
         # so we need to calculate the total microseconds ourselves
-        delta_microseconds = delta.days * (24 * 3600) + delta.seconds * 10**6 + delta.microseconds
+        delta_microseconds = delta.days * (24 * 3600 * 10**6) + delta.seconds * 10**6 + delta.microseconds
         return create_time_span(0, 0, 0, 0, 0, delta_microseconds)
 
     return x - timedelta(microseconds=total_microseconds(y))
@@ -237,17 +237,6 @@ def try_parse(string: str, style: int, unsigned: bool, bitsize: int, defValue: F
         return False
 
 
-def add(d: datetime, ts: int) -> datetime:
-    new_date = d + timedelta(milliseconds=ts)
-    if d.tzinfo:
-        old_tz_offset = d.utcoffset()
-        new_tz_offset = new_date.utcoffset()
-        if old_tz_offset is not None and new_tz_offset is not None and old_tz_offset != new_tz_offset:
-            return new_date + (new_tz_offset - old_tz_offset)
-
-    return new_date
-
-
 def add_milliseconds(d: datetime, v: int) -> datetime:
     return d + timedelta(milliseconds=v)