Date and time tools
Date Calculator
Add or subtract days, weeks, months, or years from a date locally in your browser.
Add or subtract days, weeks, months, or years from a date. Calculations use UTC calendar days.
Calculations run locally in your browser; your dates are not uploaded or stored.
Find a future or past date from a starting point.
Enter a start date, choose to add or subtract, then pick an amount and unit (days, weeks, months, or years). The calculator uses UTC calendar days so daylight-saving transitions do not change the result. Everything runs locally in your browser; your dates are not uploaded or stored.
Frequently Asked Questions
Everything you need to know about this tool, how it works, and privacy.
How does the date calculator work?
Enter a start date in YYYY-MM-DD format, choose to add or subtract, enter an amount, and select a unit (days, weeks, months, or years). The calculator returns the resulting date using UTC calendar arithmetic.
How are months and years handled?
When adding or subtracting months, the calculator adjusts the month value and lets the Date object handle rollover (for example, adding one month to January 31 gives February 28 or 29 depending on the year). Years are handled similarly by adjusting the year value.
Do time zones or daylight saving affect the result?
No. All calculations use UTC calendar days, so daylight-saving transitions and local time zones do not change the result.
Do my dates stay private?
Yes. The calculation and copy action run locally in your browser. CodeASystem does not upload or store the dates you enter.