Cron explain

Plain-language reading of a cron string plus the next runs. Five-field and Quartz six-field.

WHAT IT WILL NOT DO

Jenkins H and Quartz W/LW are refused: they need a job name or a calendar.
Times use your browser zone or UTC, not the server TZ. For a named zone, use F01.
On daylight-saving days a skipped time is omitted and a repeated hour is listed once.