date
TLDR
Show current date and time
SYNOPSIS
date [options] [+format]
DESCRIPTION
date displays or sets the system date and time. It supports various output formats, time calculations, and conversions. The command is essential for timestamping, logging, and time-based operations.
The tool is one of the most commonly used Unix utilities.
PARAMETERS
-d, --date=string
Display specified date/time-s, --set=string
Set system date/time (requires root)-u, --utc
Print/set UTC time-r, --reference=file
Display file's modification time-I[timespec]
ISO 8601 format-R, --rfc-email
RFC 5322 format
FORMAT SPECIFIERS
Date:
- %Y - Year (2024)
- %y - Year (24)
- %m - Month (01-12)
- %d - Day (01-31)
- %B - Month name (January)
- %b - Short month (Jan)
- %A - Weekday (Monday)
- %a - Short weekday (Mon)
Time:
- %H - Hour 24h (00-23)
- %I - Hour 12h (01-12)
- %M - Minute (00-59)
- %S - Second (00-59)
- %p - AM/PM
- %Z - Timezone name
Combined:
- %s - Unix epoch seconds
- %F - Full date (YYYY-MM-DD)
- %T - Full time (HH:MM:SS)
- %c - Locale's date and time
WORKFLOW
date
# ISO 8601 format
date -I
date "+%Y-%m-%d"
# Custom format
date "+%Y-%m-%d %H:%M:%S"
# Unix timestamp
date +%s
# From timestamp
date -d @1234567890
# Relative dates
date -d "tomorrow"
date -d "next monday"
date -d "2 days ago"
date -d "+3 hours"
# UTC time
date -u
# File modification time
date -r file.txt
# RFC format
date -R
RELATIVE DATES
date -d "2 weeks ago"
date -d "next friday"
date -d "last month"
date -d "3 years ago"
date -d "+5 days"
COMMON USES
Timestamped filenames:
log-$(date +%Y-%m-%d_%H-%M-%S).txt
echo "It's Monday"
fi
CAVEATS
Setting date requires root. System clock vs hardware clock different. Timezone affects output. Leap seconds not always handled. Different behavior on BSD vs GNU. Relative dates parsing can be ambiguous.
HISTORY
date has been part of Unix since Version 1 in 1971, one of the original Unix commands.
SEE ALSO
timedatectl(1), hwclock(8), cal(1)
