Calendaring from the command line
On Schedule

We take a spin through several personal calendar apps that you can manage from the command line.
If you have done any administration on a Linux system, you may have used Cron [1] or Anacron [2] for scheduling system commands. What about scheduling personal information from the command line, however? Although you could just about manage to schedule events using Cron or Anacron, free software has several more versatile applications for personal calendaring, most notably Cal or NCal [3], Calendar [4], Remind [5], and When [6].
Most of these applications are in the grand Unix tradition, focusing on a limited set of functions and are configurable in a text editor. Often, the main differences between them is the format for entering events and the syntax for a particular function, although these applications appear to borrow heavily from one another. All of these alternatives are standard in the repositories of most distributions, although only Cal is generally installed by default. Simple and quick, you may find them a welcome change after wrestling with KDE's Akonadi personal information manager or the unresponsiveness in the Google Calendar interface.
Cal and NCal
Cal and NCal provide the command-line equivalent of the date and time applet on a desktop panel that displays calendars but lacks any ability to add personal events. The main difference between Cal and NCal is that Cal organizes each month by columns, and NCal organizes by rows (Figure 1).
By itself, either command displays a calendar for the current month. However, you can display the calendar for an entire year by specifying the year as a four-digit number immediately after the basic command.
Using -A [NUMBER]
or -B[NUMBER]
, you can set the number of months to display before and after the current month. Similarly -3
displays the previous, current, and next month. By default, each week starts on Monday, but you can change the start of the week to Sunday with -S
, or back to Monday with -M
.
Calendar
Calendar looks for files called ~/calendar.[EXTENSION]
. The default calendar it looks for is calendar
, but you can use the -f [FILE]
option to specify another file, such as calendar.birthday
if you are organizing events by files.
Within a calendar file, Calendar looks for lines with the following format:
[DATE] [TAB] [EVENT DESCRIPTION]
The date is expressed in two digits for the day, month, and year, separated by a space, with a day or month assumed to come first. If the calendar file starts with a Language=[LANGUAGE]
field, then the calendar
command looks specifically for date formats that fit that locale's default format. Otherwise, almost any date format can be used, although in the case of confusion, a format is assumed to be MM DD
rather than DD MM
(Figure 2).

By default, Calendar reprints all lines for the current and next day. On Fridays, it takes into account the weekend by printing entries from Friday to Monday.
Appointments can also be defined in others ways. For example, an asterisk (*) indicates that an event takes place every month, and a day of the week means that the event occurs whenever that day occurs.
The default display of Calendar can also be modified with options, such as -A [NUMBER]
to change the number of future days that displays and -B [NUMBER]
to change the number of previous days.
Calendar is a serviceable choice, but the expectations of the date format may be a nuisance to those who prefer to start dates with a year.
Remind
Of all the applications mentioned here, Remind has by far the most options and variations. Because it does not include a preference file, many of these options have to be added to the command line.
Remind uses an event file of any name. The format for an event entry is:
REM [DAY] [DATE] +[ADVANCED WARNING] MSG [MESSAGE]
In this format, REM
signals that the line should be included when Remind prints out events, whereas the advanced warning is an optional entry for the number of days before the event that reminders should start.
Dates in an entry are varied. A two-digit year means a year between 1990 and 2075, whereas a month or a day of the week is case insensitive and can be either the full name or the first three letters as an abbreviation. A range of weekdays can be specified, or, if only a date is given, the event is mentioned every month on that date. About halfway down, Remind's man pages give 16 examples that can help you learn how dates are read.
The simplest form of command is:
remind -n [FILENAME]
The option -n
prints events in calendar format (Figure 3). Alternatives include specifying the number of months in the calendar with -c =[NUMBERS]
and displaying all events with -t
.

If anything, Remind offers more options than many users want. However, remember Remind if you are having trouble finding the exact behavior you need in a calendar application. Odds are, if any of the applications mentioned here have the options you need, Remind will have them.
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.

News
-
First Release Candidate for Linux Kernel 6.14 Now Available
Linus Torvalds has officially released the first release candidate for kernel 6.14 and it includes over 500,000 lines of modified code, making for a small release.
-
System76 Refreshes Meerkat Mini PC
If you're looking for a small form factor PC powered by Linux, System76 has exactly what you need in the Meerkat mini PC.
-
Gnome 48 Alpha Ready for Testing
The latest Gnome desktop alpha is now available with plenty of new features and improvements.
-
Wine 10 Includes Plenty to Excite Users
With its latest release, Wine has the usual crop of bug fixes and improvements, along with some exciting new features.
-
Linux Kernel 6.13 Offers Improvements for AMD/Apple Users
The latest Linux kernel is now available, and it includes plenty of improvements, especially for those who use AMD or Apple-based systems.
-
Gnome 48 Debuts New Audio Player
To date, the audio player found within the Gnome desktop has been meh at best, but with the upcoming release that all changes.
-
Plasma 6.3 Ready for Public Beta Testing
Plasma 6.3 will ship with KDE Gear 24.12.1 and KDE Frameworks 6.10, along with some new and exciting features.
-
Budgie 10.10 Scheduled for Q1 2025 with a Surprising Desktop Update
If Budgie is your desktop environment of choice, 2025 is going to be a great year for you.
-
Firefox 134 Offers Improvements for Linux Version
Fans of Linux and Firefox rejoice, as there's a new version available that includes some handy updates.
-
Serpent OS Arrives with a New Alpha Release
After months of silence, Ikey Doherty has released a new alpha for his Serpent OS.