Fixing non-second timedelta64 bug

This fixes #1738

Author: erikvansebille

parcels/tools/converters.py

@@ -54,14 +54,18 @@ class TimeConverter:
     """
 
     def __init__(self, time_origin: float | np.datetime64 | np.timedelta64 | cftime.datetime = 0):
-        self.time_origin = time_origin
         self.calendar: str | None = None
         if isinstance(time_origin, np.datetime64):
+            self.time_origin = time_origin
             self.calendar = "np_datetime64"
         elif isinstance(time_origin, np.timedelta64):
+            self.time_origin = time_origin.astype("timedelta64[s]")
             self.calendar = "np_timedelta64"
         elif isinstance(time_origin, cftime.datetime):
+            self.time_origin = time_origin
             self.calendar = time_origin.calendar
+        else:
+            self.time_origin = time_origin
 
     def reltime(self, time: TimeConverter | np.datetime64 | np.timedelta64 | cftime.datetime) -> float | npt.NDArray:
         """Method to compute the difference, in seconds, between a time and the time_origin

tests/tools/test_converters.py

@@ -40,6 +40,18 @@ def test_TimeConverter_reltime_one_day():
         assert tc.reltime(time) == ONE_DAY
 
 
+def test_TimeConverter_timedelta64_float():
+    ONE_DAY = 24 * 60 * 60
+    tc = TimeConverter(np.timedelta64(0, "s"))
+    assert tc.reltime(1 * ONE_DAY) == 1 * ONE_DAY
+
+    tc = TimeConverter(np.timedelta64(0, "D"))
+    assert tc.reltime(1 * ONE_DAY) == 1 * ONE_DAY
+
+    tc = TimeConverter(np.timedelta64(0, "ns"))
+    assert tc.reltime(1 * ONE_DAY) == 1 * ONE_DAY
+
+
 @pytest.mark.parametrize(
     "x, y",
     [