Calendar Calculation Examples

Mental Math · Axiom Academy

EXAMPLE Calendar Calculation Examples Master the art of determining the day of the week for any date Excellent work! You've completed this calendar calculation. Here's what we learned: Year Code Formula: Take last 2 digits of year, add floor(year/4), reduce mod 7. For 1776: 76 + 19 = 95, and 95 mod 7 = 4 Month Codes: Each month has a fixed code (Jan=0, Feb=3, Mar=3, Apr=6, May=1, Jun=4, Jul=6, Aug=2, Sep=5, Oct=0, Nov=3, Dec=5). Remember to adjust for leap years! Final Calculation: Sum (year code + month code + day) mod 7, then convert to day name (0=Sunday, 1=Monday, etc.) Century Adjustment: For dates before 1900 or after 2000, you need to add a century code to the calculation With practice, you'll be able to calculate the day of the week for any date in history mentally!

This is the written version of the interactive lesson above. See the full Mental Math course.