Calendar - Day of the week simplified solution
- A week is 7 days (Monday as the first day)
- Regular year: 365 days
- Leap year: 366 days
- Leap year rules:
- Years divisible by 4 are leap years.
- Century years (divisible by 100) ARE NOT leap years.
- Exception: Century years divisible by 400 ARE leap years (example: 1700, 1800, and 1900 weren’t leap years, but 2000 was).
- And ofcourse, the year divides into 12 months: [31, 28/29 (for leap years), 31, 30, 31, 30, 31, 31, 30, 31, 30, 31] days.
- https://www.calendar.com/blog/gregorian-calendar-facts/
- https://www.amazon.com/Calendrical-Calculations-Ultimate-Edward-Reingold/dp/1107683165
OxCal calendar system used for radiocarbon dating, assumes January 1, 1 AD (listed as AD 0001 in the table) was a Monday in the Gregorian calendar.