Support datetimes without microseconds (#37)

* Support datetimes without microseconds

* changelog

CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Removed
 - [issues/7](https://github.com/podaac/bignbit/issues/15): Remove the wait for GITC response
 ### Fixed
+- [issues/36](https://github.com/podaac/bignbit/issues/36): Support datetimes without microseconds
 ### Security
 
 ### Added

bignbit/generate_image_metadata.py

@@ -268,8 +268,8 @@ def extract_granule_dates(granule_umm_json: dict) -> (str, str, str, str):
     """
     time_range_dict = granule_umm_json['TemporalExtent']['RangeDateTime']
 
-    beginning_time_dt = datetime.strptime(time_range_dict["BeginningDateTime"], "%Y-%m-%dT%H:%M:%S.%fZ")
-    ending_time_dt = datetime.strptime(time_range_dict["EndingDateTime"], "%Y-%m-%dT%H:%M:%S.%fZ")
+    beginning_time_dt = parse_datetime(time_range_dict["BeginningDateTime"])
+    ending_time_dt = parse_datetime(time_range_dict["EndingDateTime"])
     middle_time_dt = beginning_time_dt + (ending_time_dt - beginning_time_dt) / 2
 
     begin = beginning_time_dt.strftime("%Y-%m-%dT%H:%M:%S.%fZ")
@@ -283,6 +283,13 @@ def extract_granule_dates(granule_umm_json: dict) -> (str, str, str, str):
     return begin, mid, end, dataday
 
 
+def parse_datetime(datetime_str: str) -> datetime:
+    try:
+        return datetime.strptime(datetime_str, "%Y-%m-%dT%H:%M:%S.%fZ")
+    except ValueError:
+        return datetime.strptime(datetime_str, "%Y-%m-%dT%H:%M:%SZ")
+
+
 def create_metadata_xml(beginning_time: str, middle_time: str, ending_time: str, dataday: str,
                         partial_id: str = None) -> ET.ElementTree:
     """