Ensure that the timezone doesn't leak into zips.

When using SOURCE_DATE_EPOCH, previous code was using time.localtime
which is affected by the system timezone.  The test code here with tzset
likely does not demonstrate the problem on Windows, but hopefully is
just a no-op there.

repro_zipfile.py

@@ -21,7 +21,7 @@ def date_time() -> Union[time.struct_time, Tuple[int, int, int, int, int, int]]:
     """
     source_date_epoch = os.environ.get("SOURCE_DATE_EPOCH", None)
     if source_date_epoch is not None:
-        return time.localtime(int(source_date_epoch))
+        return time.gmtime(int(source_date_epoch))
     return (1980, 1, 1, 0, 0, 0)
 
 

tests/test_core.py

@@ -1,5 +1,5 @@
 import platform
-from time import sleep
+from time import sleep, tzset
 from zipfile import ZipFile, ZipInfo
 
 from repro_zipfile import ReproducibleZipFile
@@ -195,6 +195,8 @@ def test_write_single_file_source_date_epoch(base_path, monkeypatch):
         zp.write(data_file)
 
     monkeypatch.setenv("SOURCE_DATE_EPOCH", "1691732367")
+    monkeypatch.setenv("TZ", "America/Chicago")
+    tzset()
 
     # With SOURCE_DATE_EPOCH set
     arc_sde1 = base_path / "with_sde1.zip"
@@ -203,6 +205,8 @@ def test_write_single_file_source_date_epoch(base_path, monkeypatch):
 
     sleep(2)
     data_file.touch()
+    monkeypatch.setenv("TZ", "America/Los_Angeles")
+    tzset()
 
     arc_sde2 = base_path / "with_sde2.zip"
     with ReproducibleZipFile(arc_sde2, "w") as zp: