The calculator returns the ISO date and day of the week.
Date & Time calculator
Add or Subtract Date Calculator
Move a date forward or backward without manually counting calendar pages.
Calculated privately on your device
No account. Formula and assumptions are shown below.
Calculator inputs
Date offset details
Formula & disclaimer
Calculated Date = Start Date Β± Whole Days, Weeks, Calendar Months or Calendar Years
View assumptionsFormula reviewCalcs at Hand Editorial TeamVerified 28 August 2026 Β· automated checks included
Saved on this device
Resultβ
Projection
Move across the chart, drag the slider, or use the arrow keys.
Formula & details
Calculation
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How to read this result
Three useful checks, kept deliberately short.
Add 30 days to 28 August 2026: Choose the start date Β· Select Add and Days Β· Enter 30.
The calculation uses dates only and avoids daylight-saving time shifts.
Formula and assumptions
Calculated Date = Start Date Β± Whole Days, Weeks, Calendar Months or Calendar YearsDays and weeks use exact calendar-day increments. Months and years preserve the day where possible and otherwise use the last valid day of the destination month.
Keep in mind: Calendar results use the Gregorian calendar and do not automatically exclude weekends or holidays.
Produced byCalcs at Hand Editorial Team
Last formula check28 August 2026
Review methodKnown examples + boundary cases
Editorial and correction policy β