Read a cron expression in a sentence, see the next six times it fires in your own zone, and start from a preset if the fields are the part you never remember.
The standard five: minute, hour, day of month, month and weekday. Seconds, @yearly aliases and the L and W extensions are refused rather than guessed at, because they are not portable.
Because cron treats them as or, not and, whenever both are restricted. 0 12 13 * fri runs every Friday and on the 13th, which is the rule that surprises almost everyone.
Yours, as the browser reports it. A cron on a server runs in that server's zone, which is UTC unless somebody changed it, and that gap is where most missed jobs come from.
In a zone with daylight saving, a job scheduled at 02:30 can run twice in autumn and not at all in spring. Run anything that must happen exactly once in UTC, or pick a time outside the change window, which in most zones is between 01:00 and 03:00.