date

What it does

How to write it

date [OPTION]... [+FORMAT]
date [-u] -s "DATE TIME"

Main parts

%F

Date: 2026-10-25.

%T

Time: 11:42:10.

%Y %m %d

Year, month, day.

%H %M %S

Hour, minute, second.

%s

Seconds since 1970-01-01 UTC (epoch).

%a %A / %b %B

Short/long day name / month name.

%j

Day of the year.

%u

Day of the week (1 = Monday).

%V

ISO week number.

%z %Z

Time zone offset / name.

%N

Nanoseconds.

Most used

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$ run as a normal user# run as root (or with sudo)

1. 1Now

   $date
   Sun Oct 25 11:42:10 +03 2026

   Local time zone.

2. 2A file-name friendly stamp

   $tar -czf /backup/etc-$(date +%F_%H%M).tgz /etc

   etc-2026-10-25_1142.tgz.

3. 3UTC

   $date -u

   Same moment in UTC (logs from many servers).

4. 4Calculate dates

   $date -d '+30 days' +%F
   $date -d 'last friday' +%F

   Expiry dates for chage -E.

5. 5Epoch seconds

   $date +%s
   1761381730
   $date -d @1761381730

   Convert log time stamps.

6. 6ISO format

   $date -Iseconds
   2026-10-25T11:42:10+03:00

   For JSON and APIs.

7. 7Time of a file change

   $date -r /etc/passwd

   When was a user changed?

8. 8Time in another zone

   $TZ=Europe/Amsterdam date

   Without changing the system.

9. 9Set the clock (lab without NTP)

   #timedatectl set-ntp false; date -s "2026-10-25 12:00:00"

   With NTP on, chrony corrects it.

10. 10Days until a certificate expires (security)

    $echo $(( ( $(date -d "$(openssl x509 -enddate -noout -in /etc/pki/tls/certs/site.crt | cut -d= -f2)" +%s) - $(date +%s) ) / 86400 ))

    Alert when it gets low.

11. 11Measure how long something takes

    $S=$(date +%s); sleep 2; echo "took $(( $(date +%s) - S )) s"

    Simple timing in scripts.

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Exit codes