Date/Time

System time and timezone information.

Enumerate

Date/Time Info

date	Display the current date and time
date +"%Y-%m-%d %H:%M:%S %Z"	Custom format: YYYY-MM-DD HH:MM:SS TZ
hwclock	Displays hardware clock time (if different from system time).
hwclock --show	Displays the hardware clock time.
timedatectl	Displays current timezone and other time-related settings.
ntpq -p	Displays current NTP synchronization status.
uptime	Shows system uptime and load averages.
date +%s	Current Epoch Time (Seconds from January 1, 1970).
cal	Displays a calendar for the current month.

Timezone Info

cat /etc/timezone	Displays the system's timezone (Debian-based systems).
ls /usr/share/zoneinfo	Lists available timezones.
timedatectl list-timezones	Lists all timezones (systemd systems).
date +%Z	Shows the timezone abbreviation.
zdump /etc/localtime	Shows the timezone based on the /etc/localtime file.
TZ='America/New_York' date	Displays date/time info for specified timezone without changing system settings.

Modify

date --set="2024-02-04 15:30:00"	Sets system time and date.
sudo date --set="2024-02-04 15:30:00"	Sets system time and date with admin privileges.
hwclock --set --date="2024-02-04 15:30:00"	Sets hardware clock time (requires root access).
timedatectl set-timezone <timezone>	Sets timezone (e.g., "America/Los_Angeles").
sudo hwclock --systohc	Writes system time to hardware clock.
sudo hwclock --hctosys	Reads hardware clock time and sets system time.
ntpdate pool.ntp.org	Synchronizes time with a public NTP server.
systemctl start ntpd	Starts the NTP daemon for automatic synchronization.

Time-based Commands

timeout <seconds> <command>	Runs a command with a time limit.
watch -n <seconds> <command>	Repeatedly executes a command, showing output.

File Locations

/usr/share/zoneinfo	Timezone information directory.
/etc/timezone	Stores the system's default timezone (Debian-based systems).
/etc/localtime	A symlink or copy of the timezone information file from /usr/share/zoneinfo.
/etc/sysconfig/clock	Stores timezone settings on some Linux distributions (e.g., Red Hat-based systems).
/etc/sysconfig/timezone	Stores timezone settings on some Linux distributions (e.g., Red Hat-based systems).