Re-introduce fix removed in pydata#4684

Author: znicholls

xarray/coding/times.py

@@ -181,6 +181,11 @@ def _decode_datetime_with_pandas(flat_num_dates, units, calendar):
         # strings, in which case we fall back to using cftime
         raise OutOfBoundsDatetime
 
+    with warnings.catch_warnings():
+        warnings.filterwarnings("ignore", "invalid value encountered", RuntimeWarning)
+        pd.to_timedelta(flat_num_dates.min(), delta) + ref_date
+        pd.to_timedelta(flat_num_dates.max(), delta) + ref_date
+
     # To avoid integer overflow when converting to nanosecond units for integer
     # dtypes smaller than np.int64 cast all integer-dtype arrays to np.int64
     # (GH 2002).