cal Command Linux: Display and Manage Calendars in Terminal

The cal command is one of Linux’s most straightforward yet powerful utilities for displaying calendar information directly in your terminal. Whether you’re a system administrator scheduling tasks, a developer planning releases, or simply need to check dates quickly, the cal command provides an efficient way to view calendar data without leaving your command-line environment.

What is the cal Command?

The cal command (short for calendar) is a built-in Linux utility that displays a formatted calendar in the terminal. It can show calendars for specific months, years, or the current date, making it an essential tool for date-related operations and quick reference.

By default, cal displays the current month’s calendar with the current date highlighted, providing immediate temporal context for your work.

Basic Syntax and Usage

The basic syntax of the cal command follows this pattern:

cal [options] [month] [year]

Let’s start with the most basic usage:

cal

Output:

    August 2025
Su Mo Tu We Th Fr Sa
                1  2
 3  4  5  6  7  8  9
10 11 12 13 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30
31

The current date (25th in this example) would typically be highlighted or marked in some way depending on your terminal’s capabilities.

Displaying Specific Months and Years

Current Year, Different Month

To display a specific month of the current year:

cal 12

Output:

   December 2025
Su Mo Tu We Th Fr Sa
    1  2  3  4  5  6
 7  8  9 10 11 12 13
14 15 16 17 18 19 20
21 22 23 24 25 26 27
28 29 30 31

Specific Month and Year

To display a calendar for a specific month and year:

cal 6 2024

Output:

     June 2024
Su Mo Tu We Th Fr Sa
                   1
 2  3  4  5  6  7  8
 9 10 11 12 13 14 15
16 17 18 19 20 21 22
23 24 25 26 27 28 29
30

Entire Year Display

To view an entire year’s calendar:

cal 2025

This command displays all 12 months of 2025 in a neatly formatted grid, perfect for annual planning and overview.

Advanced Options and Flags

Monday as First Day (-m)

By default, cal displays Sunday as the first day of the week. To start with Monday:

cal -m

Output:

    August 2025
Mo Tu We Th Fr Sa Su
             1  2  3
 4  5  6  7  8  9 10
11 12 13 14 15 16 17
18 19 20 21 22 23 24
25 26 27 28 29 30 31

Three Month Display (-3)

Display the previous, current, and next month:

cal -3

This shows a three-month view centered on the current month, excellent for short-term planning.

Julian Day Numbers (-j)

Display Julian day numbers (day of year):

cal -j

Output:

        August 2025
Sun Mon Tue Wed Thu Fri Sat
                214 215
216 217 218 219 220 221 222
223 224 225 226 227 228 229
230 231 232 233 234 235 236
237 238 239 240 241 242 243

Year Display (-y)

Display the entire current year:

cal -y

This is equivalent to cal $(date +%Y) and shows all months of the current year.

Practical Examples and Use Cases

Planning and Scheduling

Check what day of the week a specific date falls on:

cal 12 2025

This helps when planning events or checking historical dates.

Quick Date Verification

Verify the number of days in February for leap years:

cal 2 2024  # Leap year
cal 2 2025  # Regular year

Historical Date Research

Check historical dates:

cal 7 1969  # Month of moon landing
cal 12 1999 # Y2K preparation month

Integration with Other Commands

Combining with Date Command

Get the current month with highlighted today:

cal $(date +%m) $(date +%Y)

Piping and Formatting

Save calendar output to a file:

cal 2025 > calendar_2025.txt

Using in Scripts

Create a script to show upcoming months:

#!/bin/bash
echo "Current and next two months:"
cal -3

Troubleshooting Common Issues

Invalid Date Ranges

The cal command has limitations on date ranges. Most systems support years from 1 to 9999:

cal 1 1     # January of year 1
cal 12 9999 # December of year 9999

Locale and Language Settings

Calendar display depends on your system’s locale. To check different locales:

LANG=en_US cal     # English
LANG=es_ES cal     # Spanish (if available)

Terminal Width Issues

If your terminal is too narrow, the year view might not display properly. Ensure your terminal is at least 80 characters wide for optimal viewing.

Alternative Calendar Tools

While cal is the standard tool, you might also encounter:

• ncal: An alternative calendar program with different formatting
• gcal: GNU calendar with more features
• calendar: BSD calendar program with reminder capabilities

Tips for Efficient Usage

Creating Aliases

Add useful aliases to your shell configuration:

# In .bashrc or .zshrc
alias cal3='cal -3'
alias caly='cal -y'
alias calm='cal -m'

Quick Reference Functions

Create functions for common tasks:

function whatday() {
    cal $2 $1 | grep -E "(^|[^0-9])$3([^0-9]|$)"
}

Best Practices

1. Use -m flag if you prefer Monday-first calendars for business planning
2. Combine with other commands for automated date processing
3. Redirect output when creating documentation or reports
4. Consider terminal width when using in scripts or automated environments

Conclusion

The cal command is a simple yet versatile tool that every Linux user should master. From quick date checks to historical research and planning, it provides immediate access to calendar information without the need for external applications or internet connectivity.

Whether you’re scheduling cron jobs, planning project timelines, or simply checking when the weekend starts, the cal command offers a reliable, fast, and always-available solution. Its simplicity makes it perfect for both interactive use and scripting applications, making it an indispensable part of the Linux command-line toolkit.

Practice with different options and integrate cal into your daily workflow to maximize productivity and maintain better temporal awareness in your Linux environment.