Calcol is a wrapper around the cal command from util-linux that allows you to display a colorized calendar. Since 2023, cal can be colorized:

util-linux/util-linux#2053

but months and week headers cannot be customized separately, and colored headers straddle separate months.

Calcol arguably looks a bit better, with months and week headers that can be customized independently, and header backgrounds that do not straddle separate months. Calcol also allows you to customize year numbers, and accepts terminal colors in the 0-255 range instead of being limited to the 16 ANSI colors.

An example of differences between cal and calcol can be seen in this screenshot:

Another example, this time with a vertical display (-v option) on a light background:

TLDR: Use calcol if you prefer its looks; cal and calcol are equally easy to configure.

A POSIX system with cal and awk.

1. Download the provided calcol.sh file.

2. Make the file executable (chmod +x calcol.sh) and copy it into your PATH.

3. Alias cal to calcol.sh in your .bashrc or equivalent:

alias cal='calcol.sh'

If you want weeks to start on monday, use:

alias cal='calcol.sh -m'

as an aliasing command. If you want weeks to start on sunday, use:

alias cal='calcol.sh -s'

If your version of cal is already configured with custom colors, please remove or rename your terminal-colors.d/cal.scheme config file; otherwise calcol won't function correctly, as it expects non-colorized text input from cal.

Calcol can be customized via environment variables:

CALCOL_SAT and CALCOL_SUN should contain cal's abbreviations for Saturday and Sunday, respectively. Their default values are "Sat" and "Sun," so leave them untouched if your version of cal uses English. If your version of cal uses another language, however, you should define CALCOL_SAT and CALCOL_SUN so that they equal the abbreviations actually employed. In French, for example, these abbreviations are "Sa" and "Di," so you should write the following in your .bashrc or equivalent:

    CALCOL_SAT=Sa
    export CALCOL_SAT

    CALCOL_SUN=Di
    export CALCOL_SUN

Getting these values right is important, because calcol uses them to detect calendar settings and text positions to be colorized.

The other environment variables for calcol are used to customize colors. These variables specify the colors for week headers, month names, weekend days, week numbers, year names, and focus (i.e., the current day). The format for a custom color specification is:

    foreground,background,attribute

Foreground and background are optional color numbers from 0 to 255. The optional attribute is either "b" (for bold) or "u" (for underline). Trailing commas can be deleted (e.g., see the entry for CALCOL_WEEKEND in the table above).

For example, CALCOL_MONTH equals ",,b" by default, meaning that month names appear in bold ("b") with no background color. To make month names appear in color 252, on background 140, and underlined, write the following in your .bashrc or equivalent:

    CALCOL_MONTH=252,140,u
    export CALCOL_MONTH

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