ISO8601 $ man date -I[TIMESPEC], --iso-8601[=TIMESPEC] output date/time in ISO 8601 format. TIMESPEC='date' for date only (the default), 'hours', 'minutes', 'seconds', or 'ns' for date and time to the indicated precision. $ date --iso-8601 2023-01-22 $ date --iso-8601=date 2023-01-22 $ date --iso-8601=hours 2023-01-22T14+0900 $ date --iso-8601=minutes 2023-01-22T14:01+0900 $ date --iso-8601=seco..