mariadb-binlog --start/stop-datetime incorrectly accepts over-max timestamps

mariadb-binlog's --start-datetime and --stop-datetime options accept timetamps beyond the Epocalypse (Y2038 before MDEV-32188, Y2106 after) with no error or warning.
Additionally, those timestamps incorrectly behave similar to a minimum timestamp rather than a maximum:

• --start-datetime '6789-10-01 12:34' outputs the entire file rather than skipping most (if not all) events.
• --stop-datetime '6789-10-01 12:34' outputs no events (as if the file is empty) rather than all of them.