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DENeed more explanation? Explore our learning booklets at Singer Shamrock.
Four training stages · one method
A date. Its weekday.
Learn to work out a weekday in your head. Start with your birthday, discover the calendar’s patterns and practise one step at a time.
12 December 1981 was a Saturday. Two weeks later, 26 December was also a Saturday. So 25 December was a Friday. That is the idea: start from a known date and count the days.
Start here: century anchorsFree · No account · Practise at your own pace
More confidence with numbers — at work, in education and everyday life.
Century anchors
Remember 1643: four anchors that repeat every 400 years.
02 · ShortcutThe year anchor
Subtract 28, 56 or 84 first. Then find the weekday shared by the year’s anchor dates.
03 · ConnectionMonth anchors
Learn the reference dates and count forwards or backwards to your date.
04 · All togetherFull BDAY
Combine the steps, then try calculating the whole date in your head.
BDAYMETHOD
What day was your birthday?
Enter any valid date. See the weekday and open the worked solution.
Gregorian calendar, years 1–9999. Earlier dates are calculated using Gregorian rules extended backwards; historical local calendars may differ.
Two tools. One direction.
Use Bdaymethod to practise with dates and BRATS11 to explore mental arithmetic. The shared booklet will guide you through both methods with examples and exercises.
Discover BRATS11 ↗Bdaymethod uses John Conway’s Doomsday algorithm. Here, “BDAY” is the name for the birthday-friendly learning approach and the year’s shared anchor weekday.