The intent of the implementation clearly is to allow parsing time first,
date second. But this failed, because a time such as "14:30:15" would
successfully parse as a date (as 14th of current month, current year).
Consequently an attempt is made to parse the actual date as time, which
fails, and therefore the whole ParseDateTime() fails.
Adding a failing test case for ensuring times cannot be parsed as dates
does not cause a failure, because partially yet successfully parsed inputs
get silently ignored (in both ParseDate and ParseDateTime tests). Fixing
both of these, too.
Closes#22203.
504c0b16c3