The midnight day-shift section is the part most guides skip — it is easy to fix the hour and still fire a day late because the weekday field moved with the UTC date. Your conversion table makes the half-hour trap concrete too; subtracting 5 instead of 5:30 is exactly the kind of error that looks right until a 9 PM job runs at 8:30. I also appreciated the CRON_TZ warning, since that advice shows up everywhere and quietly does not work on Debian and Ubuntu.