This calendar is designed for use in Minecraft Java Edition.

PDF Link (Download it for clearer detail and offline availability): 1drv.ms/b/s!AtxLP-yySPF4enyxDLa8K_GjDNc?e=2VyAJ1

NOTE: This is NOT a Mod/Plugin/Datapack, the PDF above are just set of instructions about the calendar (Number of Day/Months, Calculation Formulas, etc), the compatible versions mentioned below are the versions that have the "features that the calendar are dependent on" (like, the number of days passed in F3 debug screen, lunar cycle, game ticks, etc) that remains unchanged or not removed.

The calendar is compatible in versions (I keep this list updated if I can):

1.18.2
1.18.1
1.18
1.17.1
1.17
1.16.5
1.16.4
1.16.3
1.16.2
1.16.1
1.16
1.15.2
1.15.1
1.15
1.14.4
1.14.3
1.14.2
1.14.1
1.14
1.13.2
1.13.1
1.13
1.12.2
1.12.1
1.12
1.11.2
1.11.1
1.11
1.10.2
1.10.1
1.10
1.9.4
1.9.3
1.9.2
1.9.1
1.9
1.8.9
1.8.8
1.8.7
1.8.6
1.8.5
1.8.4
1.8.3
1.8.2
1.8.1
1.8 (starting on snapshot 14w06a)