Birthday Calculator
Looking backward at the birth date
Enter a birth date to see the weekday and calendar details tied to that date. The calculation works from the date itself; it does not need to know the person’s current age or next birthday.
Weekdays repeat on a seven-day cycle, while leap years shift later anniversaries by an additional day. The calculator handles those calendar rules automatically.
The 29 February edge case
A 29 February birth date is a valid date only in a leap year. The original birth date never changes; questions about which day counts as the anniversary in an ordinary year can depend on local custom or law, so this page keeps the historical date separate from the next-birthday countdown.
Questions people ask
What if the birth date is 29 February?
The original birth date remains 29 February. Anniversary conventions in non-leap years can differ by place or purpose, so this page keeps the historical date separate from the countdown convention.