Birthday CalculatorWhat day was I born, and how many days until my next birthday?
Find the weekday you were born on, a live countdown to your next birthday, the age you will turn, your birthstone, and the weekday of each of your next 10 birthdays.
- Live countdown
- Leap-day aware
- 10-year weekday strip
- Shareable link
Birthday calculator
Next birthday
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Your next 10 birthdays
Weekend birthdays are highlighted, so you can spot the years for a big party.
How do I find out what day of the week I was born?
Enter your date of birth and the calculator shows the weekday instantly. Someone born on March 21, 1998 was born on a Saturday. The calculator also counts down to your next birthday, shows the age you will turn, your birthstone, and the weekday of each of your next 10 birthdays.
How the birthday calculator works
- Weekday of birth: worked out from the Gregorian calendar for any date. Every leap-year rule is applied, including the century rule.
- Next birthday: your birthday this year if it hasn’t passed yet, otherwise next year’s. The countdown runs to midnight local time.
- Leap-day birthdays: people born on February 29 choose whether they celebrate on February 28 or March 1 in common years.
- 10-year strip: a birthday moves forward one weekday each year (two after a leap day). That’s why a weekend birthday comes around only every few years.
Why your birthday moves one weekday each year
A common year has 365 days, which is 52 weeks plus 1 day. So the same date falls one weekday later the next year. Crossing a February 29 adds a second day. A birthday on Tuesday this year will usually fall on Wednesday next year, and jumps to Thursday when a leap day falls in between. Over 28 years the pattern repeats.
Fun fact: about 1 in 1,461 people is born on February 29 (one leap day every 4 × 365 + 1 days). That makes roughly 5 million “leaplings” worldwide.
Birthstones by month
Modern birthstone list as published by the American Gem Society. Some months have more than one traditional stone.
| Birth month | Birthstone |
|---|---|
| January | Garnet |
| February | Amethyst |
| March | Aquamarine, Bloodstone |
| April | Diamond |
| May | Emerald |
| June | Pearl, Alexandrite, Moonstone |
| July | Ruby |
| August | Peridot, Spinel, Sardonyx |
| September | Sapphire |
| October | Opal, Tourmaline |
| November | Topaz, Citrine |
| December | Turquoise, Tanzanite, Zircon |
Related calculators
Planning around a birthday? These calculators help:
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Manzoor Ahmad
Calculator Developer · Founder of DexoCalc
I’m a pharmacist turned web developer with 13+ years of experience building web tools. This calculator uses the same tested Gregorian date engine as the rest of DexoCalc’s date tools. I added the leap-day switch after readers born on February 29 asked for it.
Published · Last reviewed · Author profile · Report an issue
Birthday calculator: frequently asked questions
Enter your date of birth in the calculator and it shows the weekday right away. It works for any date in the Gregorian calendar. To look up the weekday of any date, not just birthdays, try the day of the week calculator.
The countdown shows days, hours, minutes and seconds until midnight at the start of your next birthday, in your own time zone.
In common years most people celebrate on February 28 or March 1. Legal rules vary by country, for example for when someone turns 18. Pick your preference with the leap-day switch.
A year is 52 weeks plus one day (two in a leap year), so each birthday shifts one weekday later, or two when a February 29 falls in between.
It depends on your birth month: January garnet, February amethyst, March aquamarine, April diamond, May emerald, June pearl, July ruby, August peridot, September sapphire, October opal, November topaz and December turquoise. Several months have alternative stones.
Yes. Add ?dob=YYYY-MM-DD to this page’s address, and the calculator opens with that birthday already filled in.
The result shows the age you turn on your next birthday. For your exact age today in years, months and days, use the age calculator.
Sources & references
- Birthstones by Month, American Gem Society
- Leap Year Explained, timeanddate.com
- ISO 8601: Date and time format, International Organization for Standardization
Countdowns use your device’s clock and time zone.