About this calculator
Dates are counted on the Gregorian calendar, which India and most of the world use.
How to use it
- Enter a date.
- Read the weekday.
The formula
Weekday = (days since a known reference date) mod 7
- Gregorian calendar
- the standard civil calendar
Worked example
India’s Independence Day
- 15 August 1947 was a Friday.
- It was day 227 of the year, in ISO week 33.
What the result means
Birthdays move forward one weekday each year, or two after a 29 February.
Assumptions
- Gregorian calendar.
Limitations
- Dates before 1582 used the Julian calendar in many places.
Frequently asked questions
What day was 15 August 1947?
Friday.
What day was I born on?
Enter your date of birth to see it.
Why does my birthday shift a day each year?
365 days is 52 weeks and 1 day.
Last reviewed on 3 October 2026. Found a mistake? Tell us.