How many days until my birthday?
Enter your date of birth to count down to your next birthday. It also shows the weekday you were born and how many days you have lived.
- Days until your birthday
- 259
Your next birthday is Tuesday, June 15, 2027 (259 days to go), when you turn 32.
- Next birthday
- Tuesday, June 15, 2027
- Countdown
- 259 days to go
- Age on that birthday
- 32
- Day you were born
- Thursday
- Age now
- 31 years, 3 months, 14 days
- Days lived
- 11,429
Answer for the example date Tuesday, September 29, 2026. It changes to today's date when the page loads.
Days until your birthday: 259. Your next birthday is Tuesday, June 15, 2027 (259 days to go), when you turn 32.
How to calculate
Counts the days to your next birthday and gives its date, the age you turn, the day of the week you were born, and your age and days lived so far.
Example with the default inputs (Date of birth June 15, 1995, Count from September 29, 2026) on the example date Tuesday, September 29, 2026: Your next birthday is Tuesday, June 15, 2027 (259 days to go), when you turn 32.
Method: next birthday = the date of birth plus the fewest whole years (at least 1) that is on or after the count-from date; days until = next birthday − count-from date.
- The next birthday is the first birthday on or after the count-from date, so on your birthday the count is 0.
- A February 29 birthday falls on February 28 in years that are not leap years.
- Dates are calendar days on the Gregorian calendar (1600 to 2400), with no time of day or time zone.
- Age is whole years, then whole months, then days; month ends clamp (January 31 plus one month is February 28 or 29).
- A date of birth after the count-from date gives no answer.
Worked examples
Each example is checked against the calculator on every build.
- Date of birth 1995-06-15, Count from 2026-09-27 gives Countdown 261 days to go, Days until your birthday 261, Next birthday 2027-06-15, Age on that birthday 32, Day you were born Thursday, Age now 31 years, 3 months, 12 days, Days lived 11,427.Source: hand calculation in content.mdx; Python: (date(2027,6,15) - date(2026,9,27)).days = 261
- Date of birth 2000-02-29, Count from 2026-09-27 gives Days until your birthday 154, Countdown 154 days to go, Next birthday 2027-02-28, Age on that birthday 27, Day you were born Tuesday.Source: hand calculation in content.mdx; Python: (date(2027,2,28) - date(2026,9,27)).days = 154
- Date of birth 1990-09-27, Count from 2026-09-27 gives Days until your birthday 0, Countdown today, Next birthday 2026-09-27, Age on that birthday 36, Age now 36 years.Source: hand calculation in content.mdx: 2026 − 1990 = 36
- Date of birth 2026-09-27, Count from 2026-09-27 gives Days until your birthday 365, Countdown 365 days to go, Next birthday 2027-09-27, Age on that birthday 1, Days lived 0.Source: hand calculation in content.mdx: September 27, 2026 to September 27, 2027 is 365 days
- Date of birth 1969-07-20, Count from 2026-12-31 gives Countdown 201 days to go, Days until your birthday 201, Next birthday 2027-07-20, Age on that birthday 58, Day you were born Sunday.Source: hand calculation in content.mdx; July 20, 1969 (the Apollo 11 Moon landing) was a Sunday; Python: date(1969,7,20).weekday() = 6 (Sunday)
How it works
Next birthday. Add whole years to your date of birth until the date is on or after the count-from date (today, unless you change it). The smallest number of years, at least 1, gives the next birthday and the age you turn. If your date of birth is February 29 and the year is not a leap year, the birthday is February 28.
Days until. The number of days from the count-from date to the next birthday. It is 0 on your birthday and at most 366. In words (the Countdown line): “today” when it is 0, “1 day to go” when it is 1, and “N days to go” otherwise.
Day you were born. The weekday of your date of birth on the Gregorian calendar, found by counting days from a date with a known weekday (January 1, 1970 was a Thursday).
Age now. Whole years, then whole months, then days, from the date of birth to the count-from date. A month end past the end of a shorter month moves to that month's last day, so January 31 plus one month is February 28 (or 29).
Days lived. The number of days from the date of birth to the count-from date.
Assumptions
- Born on the count-from date, the age line is left out (it would be 0) and days lived is 0. A next birthday can fall after 2400 (born 1600-01-01, counted from 2400-12-31: January 1, 2401); it still shows.
- Dates are whole calendar days on the Gregorian calendar, from 1600 to 2400. There is no time of day or time zone.
- Leap years: every year divisible by 4, except years divisible by 100 that are not divisible by 400.
- A date of birth after the count-from date gives no answer. Born on the count-from date, the next birthday is the first one, a year later.
Worked examples by hand
Born June 15, 1995, counted from September 27, 2026. The birthday in 2026 (June 15) has passed, so the next one is June 15, 2027, when you turn 2027 − 1995 = 32. Days: 3 (rest of September) + 31 + 30 + 31 + 31 + 28 + 31 + 30 + 31 (October to May) + 15 = 261. June 15, 1995 was a Thursday. Age now: 31 years, 3 months, 12 days; days lived: 11,427.
Born February 29, 2000, counted from September 27, 2026. 2027 is not a leap year, so the next birthday is February 28, 2027, 154 days away, when you turn 27. February 29, 2000 was a Tuesday (2000 was a leap year, because it is divisible by 400).
Born September 27, 1990, counted from September 27, 2026. The birthday is that day: 0 days, turning 36, age exactly 36 years.
Born September 27, 2026, counted from the same day. The next birthday is the first one, September 27, 2027, 365 days later (2027 has no February 29), turning 1.
Born July 20, 1969, counted from December 31, 2026. The next birthday is July 20, 2027, 201 days away, turning 58. July 20, 1969, the day of the Moon landing, was a Sunday.
Other questions people ask
How many days until my birthday?
Count the days from today to your next birthday. For a June 15 birthday, counted from September 27, 2026: 3 days left in September, then 31 + 30 + 31 + 31 + 28 + 31 + 30 + 31 days to May 31, then 15 days of June, for 261 days. The calculator counts from today unless you pick another date.
What day of the week was I born?
The page shows it under "Day you were born". It counts the days from a date with a known weekday; for example July 20, 1969, the day of the Apollo 11 Moon landing, was a Sunday.
When is my birthday if I was born on February 29?
In a leap year, on February 29. In other years this calculator uses February 28, the last day of February. Some places use March 1 for legal purposes, so check if it matters for a document.
How is my age worked out?
Whole years first, then whole months, then days. Born June 15, 1995, on September 27, 2026 you are 31 years, 3 months, and 12 days old: 31 years to June 15, 2026, 3 months to September 15, and 12 more days.
What does it show on my birthday?
0 days: the birthday is today, and the age shown is the age you turn today.
Which leap years does it count?
The Gregorian rule: a year divisible by 4 is a leap year, except years divisible by 100, which are leap years only if they are also divisible by 400. So 2000 was a leap year and 1900 was not.