timezones are now removed if present (#62)

* timezones are now removed if present

* realized I had the test using the wrong dataset

* now linted

* now apply the timezone instead of ignoring it

Author: kthyng

docs/whats_new.md

@@ -1,6 +1,10 @@
 # What's New
 
-## v0.13.0 (November 19, 2025)
+## v0.13.2 (November 20, 2025)
+
+* If timezone-aware `start_time`, `start_time_end`, or `end_time` is input, the timezone is now removed and it is assumed they are in the same timezone as the model times.
+
+## v0.13.1 (November 19, 2025)
 
 * Fixed kerchunk JSON file filtering.
 * Added CIOFS3 as ocean model option.

particle_tracking_manager/config_the_manager.py

@@ -110,12 +110,12 @@ class TheManagerConfig(BaseModel):
     )
     start_time: datetime | None = Field(
         datetime(2022, 1, 1),
-        description="Start time for drifter simulation. start_time or end_time must be input.",
+        description="Start time for drifter simulation. start_time or end_time must be input. If a timezone is included, it will be used and the time will be converted to UTC which is the same timezone as the models.",
         json_schema_extra=dict(ptm_level=1),
     )
     start_time_end: datetime | None = Field(
         None,
-        description="If used, this creates a range of start times for drifters, starting with `start_time` and ending with `start_time_end`. Drifters will be initialized linearly between the two start times.",
+        description="If used, this creates a range of start times for drifters, starting with `start_time` and ending with `start_time_end`. Drifters will be initialized linearly between the two start times. If a timezone is included, it will be used and the time will be converted to UTC which is the same timezone as the models.",
         json_schema_extra=dict(ptm_level=2),
     )
     run_forward: bool = Field(
@@ -149,7 +149,7 @@ class TheManagerConfig(BaseModel):
     )
     end_time: datetime | None = Field(
         None,
-        description="The end of the simulation. steps, end_time, or duration must be input by user. start_time or end_time must be input.",
+        description="The end of the simulation. steps, end_time, or duration must be input by user. start_time or end_time must be input. If a timezone is included, it will be used and the time will be converted to UTC which is the same timezone as the models.",
         json_schema_extra=dict(ptm_level=1),
     )
     # OceanModelEnum was created dynamically and will trigger an issue with mypy, so we suppress it
@@ -379,6 +379,41 @@ def calculate_config_times(self) -> Self:
 
         return self
 
+    @model_validator(mode="after")
+    def remove_timezone_info(self) -> Self:
+        """Remove timezone information from datetime fields."""
+        if self.start_time is not None and self.start_time.tzinfo is not None:
+            self.start_time = (
+                pd.Timestamp(self.start_time)
+                .tz_convert("UTC")
+                .tz_localize(None)
+                .to_pydatetime()
+            )
+            logger.debug(
+                f"Removed timezone info from start_time, new value is {self.start_time}."
+            )
+        if self.start_time_end is not None and self.start_time_end.tzinfo is not None:
+            self.start_time_end = (
+                pd.Timestamp(self.start_time_end)
+                .tz_convert("UTC")
+                .tz_localize(None)
+                .to_pydatetime()
+            )
+            logger.debug(
+                f"Removed timezone info from start_time_end, new value is {self.start_time_end}."
+            )
+        if self.end_time is not None and self.end_time.tzinfo is not None:
+            self.end_time = (
+                pd.Timestamp(self.end_time)
+                .tz_convert("UTC")
+                .tz_localize(None)
+                .to_pydatetime()
+            )
+            logger.debug(
+                f"Removed timezone info from end_time, new value is {self.end_time}."
+            )
+        return self
+
     @computed_field
     def ocean_model_config(self) -> OceanModelConfig:
         """Select ocean model config based on ocean_model."""

tests/test_opendrift.py

@@ -42,7 +42,40 @@
 
 ptm.config_ocean_model.register_on_the_fly(ds_info)
 
-seed_kws = dict(lon=2, lat=1.5, start_time=0, time_step=0.01)
+# ocean_model_local is False because otherwise it requires a `kerchunk_func_str`
+seed_kws = dict(lon=2, lat=1.5, start_time=0, time_step=0.01, ocean_model_local=False)
+
+
+def test_start_time_tz():
+    """Check start time timezone is removed."""
+
+    m = OpenDriftModel(
+        duration="1s",
+        start_time="1970-01-01T00:00Z",
+        lon=2,
+        lat=1.5,
+        time_step=0.01,
+        ocean_model="ONTHEFLY",
+        ocean_model_local=False,
+    )
+    m.add_reader(ds=ds)
+    assert m.config.start_time == pd.Timestamp("1970-01-01 00:00:00")
+    assert m.config.end_time == pd.Timestamp("1970-01-01 00:00:01")
+
+    m = OpenDriftModel(
+        duration="1s",
+        start_time=(pd.Timestamp("1970-01-01T00:00") - pd.Timedelta("5h")).tz_localize(
+            "US/Eastern"
+        ),
+        lon=2,
+        lat=1.5,
+        time_step=0.01,
+        ocean_model="ONTHEFLY",
+        ocean_model_local=False,
+    )
+    m.add_reader(ds=ds)
+    assert m.config.start_time == pd.Timestamp("1970-01-01 00:00:00")
+    assert m.config.end_time == pd.Timestamp("1970-01-01 00:00:01")
 
 
 def test_drop_vars_do3D_true():