I have a strange fascination with unusual clocks and calendars, and enough software skills to implement them virtually. A selection of these is here, sorted by output format.
Astronomical Julian Date
The Astronomical Julian Date is a count of days since noon ‘UTC’ on Monday, January 1, 4713 BC, proleptic Julian calendar. Obviously UTC didn’t exist back then, so I use it only to define a timezone, not the precise measurement scale.
Unfortunately, all of these are potentially a few seconds off - getting the precise meaning of the system clock is basically impossible, so I have to assume it’s unix time and apply leap seconds and the offset to terrestrial time myself.
The Discordian calendar was defined in the Principia Discordia, and a program for calculating it was included in util-linux from 1994 to 2011. When it was removed, I decided that simply wouldn’t do - I’d long been using it in my .bashrc as part of my greeting-info - and reimplemented enough of it for my needs as a shell script. It should work in any POSIX shell, not just bash!
All my computers are named after things from the Legend of Zelda series, and this server is named Termina, after the land visited in Majora’s Mask. It was obviously necessary to make some reference to this in my greeting banner, and I decided the best way to do that was to print the day of the week in the form of the ‘Dawn of The First Day’ screens. The First Day is defined as Monday, with Saturday being The Final Day and Sunday being A New Day. Again, this is a shell script, and again it should work on any POSIX shell.