date
ShellPackage: coreutils
The date and time, in the format you ask for. date -u +%Y%m%dT%H%M%SZ names a backup or a release so it sorts; date -d @1700000000 translates a Unix timestamp.
What its options do in the lessons
From the same glossary the lessons render under their commands, so the two cannot disagree.
date -I- Date in ISO 8601 form (
2026-08-06), which sorts correctly. date -s- Sets the system clock.
date -u- Prints the time in Coordinated Universal Time rather than in the machine's zone. Read beside plain
date, it is the shortest way to learn the host's offset. date -d- Reads a date given as text instead of the clock (
date -d '2026-08-15 14:00 UTC'). Used to convert a timestamp from one zone into another before comparing two sources.