Moon Phase Calculator
This tool allows you to enter specifics for your world and then get a list of moon phases for any given year. It supports multiple moons, strange-numbered months, leap months, and more. Hopefully there are enough options to make your calendar work.
Note - if you have leap days in a month insert those leap days as a leap month directly following the month they belong to. You may wish to name said 'leap month' as Month-LEAP.
How many months are in your year?
Include all leap months. Years between occurences specifically references the number of years a leap month does not occur again after occuring. For non-leap months, leave the third field empty or insert a 0.
How many moons does your world have?
The third box indicates the moon phase on day 1, year 1.
Which year do you wish to display the moon phases for?