/siberia/ - Off-topic

I am trying to invent a calendar system as a better alternative to a Grigorian calendar - with easily divisible 6-day weeks, [almost] constant length of the month and 1-to-1 correspondence between day of the month and day of the week.

I had came up with this structure: normal year has 366 days and consists out of eleven 30-day (or 5 week) months plus November that is 36 days (6 weeks) long instead. Leap year happens each eighth year and, unlike in Gregorian calendar, is actually shorter than a normal year - in it, November is the same size as other months, and thus the whole year is just 360 days long. Each 800th year is an ultra-short year - not only November in it is 30 days long, but December also ends after 24 days (4 weeks), making these years just 354 days long.

I called my calendar, without excessive modesty, "United Humanity (UH) Calendar" and took year 1601 AD as year 1 UH (for both pragmatic and ideological reasons).

Here is a Python script that is supposed to convert Gregorian dates to UH dates, but I had made a mistake somewhere, and my system breaks when trying to convert dates at least at the end of the 800-year cycles. Can someone be nice enough to show me my mistake here?