Date Duration Calculator
Add or subtract days, weeks, months, and years from any calendar date.
How to Calculate & Use the Date Duration Calculator
Add or subtract time intervals from any starting date with our free date duration calculator. Whether you are tracking pregnancy milestones, scheduling project milestones, or finding historical dates, this tool makes calculations simple. Input a starting date, select whether to add or subtract time, and define the days, weeks, months, or years to find the target date.
Input & Variable Breakdown:
- Start Date: Bounded variable used in the formulas.
- Action: Bounded variable used in the formulas.
- Years: Bounded variable used in the formulas.
- Months: Bounded variable used in the formulas.
- Weeks: Bounded variable used in the formulas.
- Days: Bounded variable used in the formulas.
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Frequently Asked Questions
Our calculator handles varying month lengths by calculating standard calendar months. If the target month has fewer days than the starting day (e.g. adding 1 month to August 31st), the calculator adjusts the target date to the last day of the target month (September 30th).
A standard pregnancy due date is calculated by adding 280 days (or 40 weeks) to the first day of the last menstrual period (LMP). You can select your LMP as the start date and add 40 weeks using this tool.
Yes. The calculator supports standard calendar mathematics across past and future eras, making it a reliable tool for historical timelines and research.