Date & Time calculator
Birthday Calculator - Age, Next Birthday, Days Until
Calculate current age, next birthday date, days until birthday, and the age being reached.
FormulaCurrent age = completed calendar years; next birthday = next yearly birth month/day on or after as-of date
Formula
Birthday countdown method
Birthday and age estimates use calendar dates. Legal age rules can depend on jurisdiction and exact time of birth.
Current age = completed calendar years; next birthday = next yearly birth month/day on or after as-of date
If birth date is 2000-07-14 and as-of date is 2026-07-14, current age is 26 and days until birthday is 0.
FAQ7 common questions for this calculator.
FAQs
Does the Birthday Calculator show days until my birthday?+
Yes. It shows the next birthday date and days remaining from the as-of date.
Does it handle birthdays today?+
Yes. If the as-of date is the birthday, days until birthday is 0.
How are February 29 birthdays handled?+
For non-leap years, February 29 birthdays are treated as February 28.
How does the Birthday Calculator calculate the result?+
For the Birthday Calculator, it uses the Birthday countdown method: Current age = completed calendar years; next birthday = next yearly birth month/day on or after as-of date. If birth date is 2000-07-14 and as-of date is 2026-07-14, current age is 26 and days until birthday is 0.
What information do I need to use the Birthday Calculator?+
For the Birthday Calculator, enter the relevant dates, times, timezone, or calendar settings requested by the form. Exact dates matter because month lengths, leap years, and boundary days can change the result.
How accurate is the Birthday Calculator?+
Birthday Calculator is accurate for the values and assumptions entered on this page. It uses the Birthday countdown method. Recheck the inputs before relying on the estimate.
What should I check before using the Birthday Calculator result?+
For the Birthday Calculator, check the date and time fields, date format, timezone, daylight-saving changes, inclusive or exclusive endpoints, and whether weekends or holidays should count.
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How to use the Birthday Calculator
Calculate current age, next birthday date, days until birthday, and the age being reached. The page also explains the birthday countdown method and shows a practical example: If birth date is 2000-07-14 and as-of date is 2026-07-14, current age is 26 and days until birthday is 0.
- 1
Enter your details
Enter the values for the birthday calculator scenario you want to check.
- 2
Check the calculation
Review the result alongside the birthday countdown method: Current age = completed calendar years; next birthday = next yearly birth month/day on or after as-of date.
- 3
Compare scenarios
Change one or more inputs to see how they affect the birthday Calculator result before you use the estimate.