Library not returning datetime when valid datetime is available from battery-backed RTC on Ultimate GPS Featherwing

Issue is discussed in detail on the Adafruit forum here:
[https://forums.adafruit.com/viewtopic.php?t=204255](url)

The datetime can be parsed from the serial data returned by the GPS module, but as it is marked as invalid (V-marker?) due to having no GPS data, it is ignored by the library. The suggested improvement would be to examine the contents of the data whenever datetime is requested to see if there is a valid datetime, regardless of the validity marking.

Current workaround is to manually parse the serial data within the code, rather than relying on the library.

First inspect linked pull request #115 and the library's datetime request path, then trace how serial-data validity is handled. Done means the library returns a usable datetime from the battery-backed RTC even when the GPS validity marker is invalid, eliminating the manual parsing workaround.

Written by the indexing model from the issue text.