Adds or subtracts days, weeks, months, or years from a date.
The date arithmetic calculator adds or subtracts a given number of days, weeks, months, or years to a starting date, returning the resulting date.
Result date = Start date ± (quantity × unit) Month addition handles end-of-month: adding 1 month to 31 Jan → 28/29 Feb.
Start: 20 November 2025. Add 6 weeks (42 days) → 1 January 2026. Or add 3 months → 20 February 2026.
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