MNT: Update code to remove warnings for datetime and pandas. (#878)

* MNT: Update code to remove warnings for datetime and pandas.

* FIX: Timezone not timedelta.

act/io/arm.py

@@ -5,14 +5,14 @@
 """
 
 import copy
-import datetime as dt
 import glob
 import json
 import re
 import tarfile
 import tempfile
 import urllib
 import warnings
+from datetime import datetime, timezone
 from os import PathLike
 from pathlib import Path, PosixPath
 
@@ -766,7 +766,7 @@ def write_netcdf(
             except KeyError:
                 pass
 
-        current_time = dt.datetime.utcnow().replace(microsecond=0)
+        current_time = datetime.now(timezone.utc).replace(microsecond=0)
         history_value = (
             f'Written to file by ACT-{act.__version__} '
             f'with write_netcdf() at {current_time} UTC'

tests/plotting/test_timeseriesdisplay.py

@@ -690,7 +690,7 @@ def test_xlim_correction_plot():
 @pytest.mark.mpl_image_compare(tolerance=10)
 def test_plot_stripes():
     ds = act.io.read_arm_netcdf(sample_files.EXAMPLE_MET_WILDCARD)
-    ds = ds.resample(time='1H').mean()
+    ds = ds.resample(time='1h').mean()
     print(ds)
     reference_period = ['2019-01-01', '2019-10-02']