Parses DOS datetime into an ISO string without timezone.
DOS date format
DOS time format
An ISO datetime without timezone. Defaults to "1980-01-01T00:00:00" if the datetime is invalid
"1980-01-01T00:00:00"
https://github.com/Stuk/jszip/blob/112fcdb9953c6b9a2744afee451d73029f7cd2f8/lib/reader/DataReader.js#L105
Parses DOS datetime into an ISO string without timezone.