I've been working on this Calendar, and the underlying math is giving me a bit of trouble. I thought of another method I could use with a bit of extra flexibility in the Time measure.
This will display the day of the month of tomorrow. I have tested it a bit and so far everything works including month changes, year changes and leap years.
I'm not sure if this will help you in making your calendar since it's relative to today so every day you'll get a new 'week' displayed.