How to use the date calculator
- Choose Age to get an exact age and the next birthday, Days between dates to count days, weeks, and business days, or Add or subtract to move a date.
- Pick the dates with the date fields. Today’s date is filled in for you.
- Read the result and press the copy button next to any line to copy it.
Dates are treated as whole calendar days, so the results are the same wherever you are and never change with daylight saving. The display uses your browser’s language settings for month names and date order. Valid years run from 1 to 9999.
What you can calculate
- Your age in years, months, and days, in total months, weeks, days, and hours, and how many days until your next birthday.
- How many days, weeks, months, and business days there are between two dates, such as a project start and deadline.
- What the date will be in 30, 90, or 180 days, or in 6 weeks, 3 months, or 1 year, and what it was that long ago.
Questions
Are the dates I enter sent anywhere?
No. A date of birth is personal, so everything is calculated in your browser and nothing is uploaded or stored.
How is age in years, months, and days worked out?
The tool counts whole calendar months from the birth date up to the chosen date, then the days left over. Someone born on 15 June 2000 is 25 years, 0 months, and 0 days old on 15 June 2025, and 25 years, 0 months, and 1 day old on the 16th.
Does the day count include the start and end date?
By default the start date is counted and the end date is not, so 1 January to 2 January is 1 day. Turn on "Count the end date too" to include both days, which gives 2. Business-day totals follow the same switch.
Does the business day count remove public holidays?
No. It skips Saturdays and Sundays only, because holidays differ by country and year. Subtract any holidays that fall on weekdays in your range yourself.
What happens when I add a month to the 31st, or have a 29 February birthday?
If the new month is shorter, the date moves back to its last day, so 31 January plus 1 month is 28 February (29 in a leap year). For a 29 February birthday, the next birthday in a normal year is shown as 28 February.
Credits
Built by OneTooling using standard browser features. No third-party code runs on your data.