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Miraç Özdemir
Date & Time

Days Until Next Birthday

Enter a date of birth and today’s date to find how many days remain until the next birthday, the date of that day and the age being reached.

Version 2

Things to keep in mind:

  • The tool does not pick up today’s date by itself; you enter the reference date.
  • If today is the birthday, “days remaining” is not 0 but the days to next year’s birthday; check the “birthday today” output.
  • For 29 February births, 28 February is used in non-leap years; some official procedures treat 1 March as the date.
  • Time of day and time zones are ignored.

Calculator

Dates

Birth date of the person whose birthday you are counting down to.

The date from which the days are counted (usually today).

After the first calculation, the result updates automatically when you change a value.

Result

Enter the values and press Calculate to see the result here.

About this tool

This tool calculates the days until the next birthday from a date of birth and a reference date (usually today). It also gives the next birthday date, the age being reached and the current age.

Logic

  • The next birthday is the first month-day match after the reference date.
  • If the reference date is exactly the birthday, the next birthday is next year (365 or 366 days) and the “birthday today” flag is 1.
  • For 29 February births, 28 February is used in non-leap years.
  • Age turning = current completed age + 1.

Example: for someone born on 25 December 1990, as of 20 March 2024 the next birthday is 25 December 2024; 280 days remain and they turn 34 (current age 33). For someone born on 15 June 1990, on 15 June 2024 the remaining days are 365 and the flag “birthday today = 1” is set.

Time of day and time zones are ignored; only calendar days are counted.

Formula

  • Days remaining = next birthday date − reference date (in calendar days).
  • Current age = completed age on the reference date; age turning = current age + 1.

Extra example (29 February): for someone born on 29 February 2000, as of 1 March 2025 the next birthday is 28 February 2026 because 2026 is not a leap year; 364 days remain and they turn 26 (current age 25). As of 1 March 2027 the next birthday for the same person is 29 February 2028 (365 days).

How to read the result: “Days until next birthday” is the number of calendar days to the first birthday after the reference date; if “birthday today” is 1 the celebration is today and the days shown point to next year’s birthday. “Age turning” is the age reached on the next birthday, while “current age” is the age completed so far.

How to use

  1. Pick the date of birth.
  2. Pick the reference date (enter today).
  3. Press Calculate.
  4. Read the days remaining, the next birthday date and the age being reached.

Notes

If the reference date is the birthday, the next birthday is next year (365/366 days); the “birthday today” output shows that it is today. For 29 February births 28 February is used in non-leap years. Only calendar days are counted.

Frequently asked questions

4 questions

  1. Enter your date of birth and today’s date; the tool returns the next birthday date and the days between.

Next step

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