Date Calculator
Add or subtract exact days, weeks, months, and years to or from any starting date, calculate exact date plus duration, and find target calendar dates.
2026-08-23 + 30 Days
Target Result Date
Date Mathematics and Calendar Projection Principles
Free online date calculator. Add or subtract days, business days, weeks, months, or years to any calendar date to find past or future target dates.
Performs calendar arithmetic handling variable month lengths (28 to 31 days) and leap year day insertions.
- 1Enter your starting date.
- 2Select whether you want to Add (+) or Subtract (-) time.
- 3Input the quantity of years, months, weeks, and days.
- 4The engine immediately renders the resulting calendar date, day of the week, and ISO week number.
A contract warranty period extends 90 calendar days from March 15.
Frequently Asked Questions (FAQ)
Since February only has 28 (or 29) days, adding 1 month clamps to February 28th (or February 29th on leap years).
Enter today's date as the starting date, choose Add, and enter the number of days — the calculator instantly returns the resulting calendar date and its day of the week.
Yes — for finding the interval between two existing dates rather than projecting a new one, use the Day Counter or Date Duration calculator instead, which is built specifically for that.
Yes, subtracting follows the same clamping rule: if the target month has fewer days than the original date, the result clamps to that month's last valid day.
Yes, all four units can be combined in a single calculation — for example, adding 2 years, 3 months, and 10 days to a date in one step.
Top Similar Tools (Date & Time)
Explore more tools in Date & Time (7+ more calculators available)
Browse our complete directory with category filters, formulas, and verified engines.