Fixing leap year issue
Figured I'd just go ahead and do this. I got the toolchain all set up if you need me to build another release.
The fix is indeed very easy. The problem is that I don't fully trust current versions of DevkitPro for GBA and NDS to replicate the exact functionality as intended. There are many historical remarks of things breaking hard.
My suggestion is to find a suitable toolset that were used around the time the original tools were made, to ensure full compatibility.
Unless you can do very extensive tests using current toolsets to ensure nothing breaks, specially when we are dealing with code that could damage hardware if used improperly. The issue is so very minor that don't justify risking others hardware at all.
Feel free to provide updated binaries in your repo, if you are really that annoyed by the issue.