Fix Daylight Savings parsing
Previously the offset change for Daylight Savings was unnecessarily added all the time, resulting in this discrepancy when the local time was set to UTC-7:
Time.parse('2020-11-01 00:00:00')
=> 2020-11-01 00:00:00 -0700
Chronic.parse('2020-11-01 00:00:00')
=> 2020-11-01 01:00:00 -0700
Each time we add an offset to a base time, we need to check whether this crosses Daylight Savings boundaries. Only if it does should we adjust the time by the offset.
Closes https://github.com/mojombo/chronic/issues/147
Identified in gitlab-org/gitlab#37014 (closed)
Edited by Stan Hu