Four date calculations in one place: a D-day countdown to a target date, the difference between two dates in days, weeks and months, your age from a date of birth, and a date plus or minus a given period. Everything runs in your browser — free, no sign-up, nothing uploaded.
What can you calculate?
This date calculator offers four features: D-day, which counts the days left until a target date; Date Difference, which finds the number of days, weeks, and months between two dates; Age Calculator, which works out your age from a date of birth; and Add/Subtract Date, which adds or subtracts a period to or from a given date. It's handy for deadlines, due dates, anniversaries, and contract periods.
How to use the date calculator
- Pick a feature — choose D-day, Date Difference, Age Calculator, or Add/Subtract Date from the tabs at the top.
- Enter the date — select the reference date (or date of birth).
- Calculate — press the button and the result appears instantly.
How is D-day calculated?
It's calculated as the number of days from today to the target date. If the target is in the future it shows the days remaining (D-minus); if it's in the past it shows the days elapsed (D-plus). The calculation is based on the calendar date only and does not consider the time of day.
How is age calculated?
Age is calculated as the number of full years that have actually passed from your date of birth to today. If your birthday has already passed this year, that year is counted; if it hasn't yet, it is not — so your birthday only counts once it has passed.
How are the dates counted?
The difference is the number of full days between the start and end date, and leap years are handled automatically. Time zones and daylight-saving changes are not applied — the calculation is based purely on the calendar date.
Are weekends and holidays included?
Yes. Every calculation counts all calendar days, including weekends and public holidays. There is no option to count only business days (weekdays) or to exclude holidays.