How to Get Current Date and Time in Linux Terminal and Create Custom Commands

You need to check the current date and time, or maybe include a timestamp in a log file or backup name. What's the command, and how can you format it the way you want?

TL;DR

Use date to display the current date and time. Format it with date +"%Y-%m-%d %H:%M:%S" for custom output. Create a custom command by adding an alias to your ~/.bashrc file, like alias now='date +"%Y-%m-%d %H:%M:%S"', then run source ~/.bashrc to activate it. After that, typing now will show the formatted date and time.

The date command is your go-to tool for displaying and formatting date/time information in Linux.

The simplest usage shows the current date and time:

date

Output:

Thu Mar 28 14:23:45 UTC 2025

This default format includes the day of the week, month, day, time, timezone, and year.

Formatting the Date Output

Use the + flag followed by format specifiers to customize the output:

# Year-Month-Day format
date +"%Y-%m-%d"
# Output: 2025-03-28

# With time included
date +"%Y-%m-%d %H:%M:%S"
# Output: 2025-03-28 14:23:45

# 12-hour format with AM/PM
date +"%Y-%m-%d %I:%M:%S %p"
# Output: 2025-03-28 02:23:45 PM

Common format specifiers:

Date components:
%Y - Year (2025)
%y - Year, 2 digits (25)
%m - Month (01-12)
%d - Day of month (01-31)
%B - Full month name (March)
%b - Abbreviated month name (Mar)
%A - Full weekday name (Thursday)
%a - Abbreviated weekday name (Thu)

Time components:
%H - Hour, 24-hour format (00-23)
%I - Hour, 12-hour format (01-12)
%M - Minute (00-59)
%S - Second (00-59)
%p - AM or PM
%Z - Timezone name (UTC, EST, etc.)
%z - Timezone offset (+0000)

Special:
%s - Seconds since epoch (1711634625)

Practical Date Formats

For log files:

date +"%Y-%m-%d_%H-%M-%S"
# Output: 2025-03-28_14-23-45

For human-readable output:

date +"%B %d, %Y at %I:%M %p"
# Output: March 28, 2025 at 02:23 PM

For ISO 8601 format:

date +"%Y-%m-%dT%H:%M:%S%z"
# Output: 2025-03-28T14:23:45+0000

For backup file names (no colons or spaces):

date +"%Y%m%d_%H%M%S"
# Output: 20250328_142345

Creating a Custom Command with an Alias

Let's create a custom command called now that shows the date and time in your preferred format.

Open your shell configuration file:

nano ~/.bashrc

Add an alias at the end:

# Custom date/time command
alias now='date +"%Y-%m-%d %H:%M:%S"'

Save the file and reload your configuration:

source ~/.bashrc

Now you can use your custom command:

now

Output:

2025-03-28 14:23:45

Creating Multiple Date Aliases

You might want different formats for different purposes:

# Add these to ~/.bashrc

# Simple date
alias today='date +"%Y-%m-%d"'

# Date and time
alias now='date +"%Y-%m-%d %H:%M:%S"'

# Timestamp for filenames
alias timestamp='date +"%Y%m%d_%H%M%S"'

# Full readable format
alias fulldate='date +"%A, %B %d, %Y at %I:%M:%S %p %Z"'

After sourcing your .bashrc:

today
# Output: 2025-03-28

now
# Output: 2025-03-28 14:23:45

timestamp
# Output: 20250328_142345

fulldate
# Output: Thursday, March 28, 2025 at 02:23:45 PM UTC

Using Date in File Names

When creating backups or logs, include timestamps in filenames:

# Create a backup with timestamp
cp important.txt "important_$(date +%Y%m%d_%H%M%S).txt"

# Create a log file with today's date
touch "log_$(date +%Y-%m-%d).log"

# Create a directory with month and year
mkdir "backup_$(date +%Y_%m)"

This prevents overwriting files and makes it easy to sort by date.

Getting Time in Different Timezones

Display time in a specific timezone:

# UTC time
TZ=UTC date

# Eastern Time
TZ=America/New_York date

# Tokyo time
TZ=Asia/Tokyo date

Create aliases for frequently-used timezones:

# Add to ~/.bashrc
alias utcnow='TZ=UTC date +"%Y-%m-%d %H:%M:%S %Z"'
alias nynow='TZ=America/New_York date +"%Y-%m-%d %H:%M:%S %Z"'

Getting Unix Timestamp (Seconds Since Epoch)

For programming or logging:

date +%s
# Output: 1711634625

Create an alias for it:

# Add to ~/.bashrc
alias epoch='date +%s'

Then use:

epoch
# Output: 1711634625

Creating a Function for More Complex Commands

For more complex date formatting that needs parameters, use a function instead of an alias:

# Add to ~/.bashrc

# Function to show time in any timezone
timein() {
    if [ -z "$1" ]; then
        echo "Usage: timein <timezone>"
        echo "Example: timein America/New_York"
        return 1
    fi
    TZ="$1" date +"%Y-%m-%d %H:%M:%S %Z"
}

# Function to create dated backup of a file
backup() {
    if [ -z "$1" ]; then
        echo "Usage: backup <filename>"
        return 1
    fi
    cp "$1" "${1}.$(date +%Y%m%d_%H%M%S).bak"
    echo "Backup created: ${1}.$(date +%Y%m%d_%H%M%S).bak"
}

After sourcing your .bashrc:

timein America/Los_Angeles
# Output: 2025-03-28 07:23:45 PDT

backup important.conf
# Creates: important.conf.20250328_142345.bak

Displaying a Calendar

The cal command shows a calendar:

# Current month
cal

# Specific month and year
cal 12 2025

# Entire year
cal 2025

Create an alias for the current month with highlighted today:

# Add to ~/.bashrc
alias calendar='cal'

Practical Example: Log Entry Script

Here's a script that adds timestamped log entries:

#!/bin/bash

LOG_FILE="$HOME/activity.log"

# Function to log with timestamp
log() {
    echo "[$(date +"%Y-%m-%d %H:%M:%S")] $*" >> "$LOG_FILE"
}

# Usage
log "Started application"
log "User logged in"
log "Processing complete"

# View the log
cat "$LOG_FILE"

Output in activity.log:

[2025-03-28 14:23:45] Started application
[2025-03-28 14:23:47] User logged in
[2025-03-28 14:23:52] Processing complete

Practical Example: Automated Backup Script

A script that creates daily backups with timestamps:

#!/bin/bash

SOURCE_DIR="/var/www/app"
BACKUP_DIR="/backup"
DATE=$(date +%Y%m%d_%H%M%S)
BACKUP_FILE="$BACKUP_DIR/app_backup_$DATE.tar.gz"

# Create backup
tar -czf "$BACKUP_FILE" -C "$(dirname "$SOURCE_DIR")" "$(basename "$SOURCE_DIR")"

echo "Backup created: $BACKUP_FILE"

# Keep only last 7 days of backups
find "$BACKUP_DIR" -name "app_backup_*.tar.gz" -mtime +7 -delete

Making Aliases Available System-Wide

If you want your aliases available for all users:

# Create system-wide alias file
sudo nano /etc/profile.d/custom-aliases.sh

Add your aliases:

# System-wide date/time aliases
alias now='date +"%Y-%m-%d %H:%M:%S"'
alias today='date +"%Y-%m-%d"'

Make it executable:

sudo chmod +x /etc/profile.d/custom-aliases.sh

These aliases will be available to all users after they log in.

Checking if Your Alias Works

After adding an alias, verify it's loaded:

# List all aliases
alias

# Check specific alias
alias now

# Test it
now

If it's not working, make sure you sourced your .bashrc:

source ~/.bashrc

Or open a new terminal window.

Removing or Changing Aliases

To temporarily remove an alias in the current session:

unalias now

To permanently remove it, delete or comment out the line in ~/.bashrc:

# Open bashrc
nano ~/.bashrc

# Comment out or delete the alias line
# alias now='date +"%Y-%m-%d %H:%M:%S"'

Then source the file:

source ~/.bashrc

The date command is flexible enough for any date/time formatting you need, and creating custom aliases or functions makes your common formats just a short command away. Whether you're creating timestamped backups, logging events, or just checking the time in different formats, these techniques streamline your workflow.