Doomsday Rule Trainer - Master mental weekday calculation for any date
Show HN: How to Mentally Calculate the Day of the Week for Any Date
Learn John Conway's Doomsday Rule to mentally calculate the day of the week for any date in seconds. This interactive guide breaks the method into two secrets: the Clock of Days (modular arithmetic) and the Secret Squad (memorable anchor dates). Practice with challenges, a time machine for any year, and performance rounds to become a stage-worthy mental calculator.
Some people can hear any date and name its weekday in about two seconds. No calendar. No counting from today. Not memorization, not magic: two secrets + a little practice.