A command line tool displaying the time in a new local geocentric date format.


Geodate displays the current local time in a geocentric date format using a more natural lunisolar calendar with metric time.

Be prepared to forget all about hours and minutes and start using centidays instead!

You will also learn to get more in touch with the natural environment with this lunisolar calendar. For example the full moon will always be around the middle of every month, easy!

A detailed explanation of the date format is available online.


To install geodate from source:

$ git clone git://
$ cd geodate
$ cargo build --release
$ sudo cp target/release/geodate /usr/local/bin/


Run this tool with a longitude and a latitude as arguments and you will get a local geocentric representation of the time:

$ geodate -46.90 168.12

Add a timestamp to have the date of a particular moment (here it’s during the sunrise on the day of the summer solstice at Stonehenge):

$ geodate 51.178844 -1.826189 1403322675

Geodate can also be run in ephemeris mode:

$ geodate --ephem 51.178844 -1.826189 1403322675
Moonrise:            44:05:24:01:57
Current:             44:05:24:15:42
Sunrise:             44:05:24:15:46
Solstice:            44:05:24:44:61
Moonset:             44:05:24:58:85
Sunset:              44:05:24:84:52


Geodate implements a lot of algorithms described in the book Astronomical Algorithms by Jean Meeus to calculate the precise time of any sunrise, solstice, and new moon required to create a lunisolar calendar.

Additional astronomical events such as moonrise or equinox are also calculated in ephemeris mode.


Copyright © 2016-2017 Vincent Ollivier. Released under the MIT License.