date Command Linux: Complete Guide to Display and Set System Date

The date command is one of the most fundamental utilities in Linux systems, allowing users to display and manipulate system date and time information. Whether you’re a system administrator managing servers or a developer working with timestamps, understanding the date command is essential for effective Linux system management.

Basic Syntax of the date Command

The basic syntax of the date command follows this structure:

date [OPTION]... [+FORMAT]
date [-u|--utc|--universal] [MMDDhhmm[[CC]YY][.ss]]

Let’s start with the most basic usage – displaying the current date and time:

$ date
Mon Aug 25 07:01:23 IST 2025

Common date Command Options

Display Current Date and Time

The simplest form of the date command shows the current system date and time:

$ date
Mon Aug 25 07:01:23 IST 2025

Display UTC Time

To display time in Coordinated Universal Time (UTC), use the -u or --utc option:

$ date -u
Mon Aug 25 01:31:23 UTC 2025

$ date --utc
Mon Aug 25 01:31:23 UTC 2025

Display Date in ISO 8601 Format

For standardized date formatting, use the -I option:

$ date -I
2025-08-25

$ date -Ihours
2025-08-25T07+05:30

$ date -Iminutes
2025-08-25T07:01+05:30

$ date -Iseconds
2025-08-25T07:01:23+05:30

Date Formatting with Format Specifiers

The real power of the date command lies in its extensive formatting options. You can customize the output using format specifiers preceded by the + sign.

Year Format Specifiers

$ date "+Year: %Y, Short: %y, Century: %C"
Year: 2025, Short: 25, Century: 20

Month Format Specifiers

$ date "+Month: %B (%b) - %m"
Month: August (Aug) - 08

Day Format Specifiers

$ date "+Today is %A, %B %d, %Y (Day %j of the year)"
Today is Monday, August 25, 2025 (Day 237 of the year)

Time Format Specifiers

$ date "+Current time: %I:%M:%S %p (24h: %T)"
Current time: 07:01:23 AM (24h: 07:01:23)

Practical Date Formatting Examples

Common Date Formats

# US Format (MM/DD/YYYY)
$ date "+%m/%d/%Y"
08/25/2025

# European Format (DD/MM/YYYY)
$ date "+%d/%m/%Y"
25/08/2025

# ISO Format (YYYY-MM-DD)
$ date "+%Y-%m-%d"
2025-08-25

# Long Format
$ date "+%A, %B %d, %Y"
Monday, August 25, 2025

# Timestamp Format
$ date "+%Y-%m-%d %H:%M:%S"
2025-08-25 07:01:23

Creating Custom Formats

# File naming format
$ date "+backup_%Y%m%d_%H%M%S.tar.gz"
backup_20250825_070123.tar.gz

# Log format
$ date "+[%Y-%m-%d %H:%M:%S]"
[2025-08-25 07:01:23]

# Human readable format
$ date "+It's %I:%M %p on %A, the %d of %B, %Y"
It's 07:01 AM on Monday, the 25 of August, 2025

Working with Different Time Zones

The date command can display time in different time zones using the TZ environment variable:

# Display time in different time zones
$ TZ=UTC date
Mon Aug 25 01:31:23 UTC 2025

$ TZ=America/New_York date
Sun Aug 24 21:31:23 EDT 2025

$ TZ=Europe/London date
Mon Aug 25 02:31:23 BST 2025

$ TZ=Asia/Tokyo date
Mon Aug 25 10:31:23 JST 2025

Setting System Date and Time

Note: Setting the system date requires root privileges. Use sudo when necessary.

Setting Date Using String Format

# Set date and time (MMDDhhmm[[CC]YY][.ss])
$ sudo date 082507302025
Mon Aug 25 07:30:00 IST 2025

# Set only time (hhmmss)
$ sudo date 073000
Mon Aug 25 07:30:00 IST 2025

Setting Date Using -s Option

# Set specific date and time
$ sudo date -s "2025-08-25 07:30:00"
Mon Aug 25 07:30:00 IST 2025

# Set only date
$ sudo date -s "2025-08-25"
Mon Aug 25 00:00:00 IST 2025

# Set only time
$ sudo date -s "07:30:00"
Mon Aug 25 07:30:00 IST 2025

# Natural language (varies by system)
$ sudo date -s "next Monday"
$ sudo date -s "2 hours ago"

Getting Date from File Timestamp

You can display the modification time of a file using the -r option:

$ date -r /etc/passwd
Sun Aug 17 14:22:31 IST 2025

$ date -r /var/log/syslog "+Last modified: %Y-%m-%d at %H:%M"
Last modified: 2025-08-25 at 06:45

Date Arithmetic and Calculations

Adding and Subtracting Time

# Add days
$ date -d "today + 5 days"
Sat Aug 30 07:01:23 IST 2025

$ date -d "+5 days" "+%Y-%m-%d"
2025-08-30

# Subtract days
$ date -d "today - 10 days"
Tue Aug 15 07:01:23 IST 2025

# Add hours and minutes
$ date -d "now + 3 hours 30 minutes"
Mon Aug 25 10:31:23 IST 2025

# Complex calculations
$ date -d "next Monday + 2 weeks - 1 day"
Sun Sep 7 07:01:23 IST 2025

Working with Specific Dates

# Get day of week for specific date
$ date -d "2025-12-25" "+%A"
Thursday

# Calculate days until specific date
$ echo $(( ($(date -d "2025-12-31" +%s) - $(date +%s)) / 86400 ))
128

# Find last day of current month
$ date -d "$(date +%Y-%m-01) + 1 month - 1 day"
Sun Aug 31 00:00:00 IST 2025

Epoch Time and Timestamps

Unix Timestamp (Epoch Time)

# Get current Unix timestamp
$ date +%s
1724551283

# Convert timestamp to readable date
$ date -d "@1724551283"
Mon Aug 25 07:01:23 IST 2025

# Get timestamp with nanoseconds
$ date +%s.%N
1724551283.456789123

Practical Use Cases and Scripts

Log File Naming

#!/bin/bash
# Create log file with timestamp
LOG_FILE="/var/log/app_$(date +%Y%m%d_%H%M%S).log"
echo "Application started" > "$LOG_FILE"
echo "Log file created: $LOG_FILE"

Backup Script with Date

#!/bin/bash
# Backup with timestamp
BACKUP_DIR="/backup"
DATE_STAMP=$(date +%Y%m%d_%H%M%S)
tar -czf "${BACKUP_DIR}/backup_${DATE_STAMP}.tar.gz" /home/user/documents

Time-based Conditional Logic

#!/bin/bash
# Different actions based on time
HOUR=$(date +%H)

if [ $HOUR -lt 12 ]; then
    echo "Good morning! Current time: $(date +%I:%M %p)"
elif [ $HOUR -lt 18 ]; then
    echo "Good afternoon! Current time: $(date +%I:%M %p)"
else
    echo "Good evening! Current time: $(date +%I:%M %p)"
fi

Common date Command Flags and Options

Troubleshooting Common Issues

Permission Denied When Setting Date

If you encounter permission errors when setting the date, ensure you have root privileges:

$ date -s "2025-08-25 07:30:00"
date: cannot set date: Operation not permitted

# Solution: Use sudo
$ sudo date -s "2025-08-25 07:30:00"
Mon Aug 25 07:30:00 IST 2025

Invalid Date Format Errors

$ date -d "invalid date"
date: invalid date 'invalid date'

# Use proper format
$ date -d "2025-08-25"
Mon Aug 25 00:00:00 IST 2025

Best Practices

1. Always use UTC for servers: When managing servers across time zones, work with UTC to avoid confusion.
2. Consistent formatting: Use consistent date formats in scripts and logs for easier parsing.
3. Backup before setting: Always note the current date before changing system time.
4. Use NTP: For production systems, use Network Time Protocol (NTP) instead of manually setting time.
5. Quote complex formats: Always quote format strings containing spaces or special characters.

Integration with Other Commands

The date command works well with other Linux utilities:

# With find command
$ find /var/log -name "*.log" -newermt "$(date -d '1 week ago')"

# With touch command
$ touch -d "$(date -d 'yesterday')" oldfile.txt

# With at command
$ echo "echo 'Reminder!' | mail [email protected]" | at $(date -d 'tomorrow 9am' +%m%d%H%M%Y)

Conclusion

The Linux date command is an incredibly versatile tool that goes far beyond simply displaying the current date and time. From formatting output for logs and scripts to performing date arithmetic and setting system time, mastering the date command is essential for effective Linux system administration and scripting.

Whether you’re creating timestamped backups, parsing log files, or building time-aware applications, the examples and techniques covered in this guide provide a solid foundation for working with dates and times in Linux environments. Practice these commands and incorporate them into your daily workflows to become more efficient with Linux system management.