Birthday Calculator
Find age, birth weekday and the next birthday from a date of birth.
Calculator
Results
How it works
Find age, birth weekday and the next birthday from a date of birth.
Example
| Example | Result |
|---|---|
| A May 20, 1990 birth date has a May 20, 2026 birthday and turns 36. | See calculator |
Important notes
- Calendar calculations use Gregorian calendar rules.
- Business-day calculations exclude Saturday and Sunday unless stated otherwise.
- Time-zone calculations depend on the browser's IANA time-zone data.
- For planning purposes, verify dates and times when a contractual or legal deadline is involved.
Frequently Asked Questions
What if the birthday is February 29?
Non-leap-year handling requires a convention; this calculator follows the JavaScript date normalization for that calendar date.
How to use this calculator
What to enter
Enter or select the following as requested: Date of birth; Reference year. Follow the units, valid ranges, examples, and options displayed beside each field.
What the result means
The date or duration result is calculated from the entered dates, times, calendar rules, and exclusions. Check inclusive versus exclusive counting, time zone, daylight-saving changes, and whether weekends or holidays are excluded.
When to use it
Use this to plan a date, measure elapsed time, or estimate a deadline. Verify the relevant calendar, location, and legal or workplace rules when they affect the answer.