How are month additions handled on dates like Jan 31?

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Add / Subtract Days Calculator

Add or subtract days, weeks, months, or years from any date. Computes target calendar day or business day.

Calculation Parameters

Starting Date

Action

Amount (30)

Time Unit

Count working business days only (skip Saturdays & Sundays)

Calculated Target Date

2026-10-23

Friday, October 23, 2026 (Friday). ISO Week #43, Day 296 of the year.

Day of the WeekFriday

ISO Week NumberWeek 43

Day of the YearDay 296

Total Shift+30 days

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Pick starting date on the calendar.

Enter number of days, weeks, months, or years to add or subtract.

See resulting date, day of week, and ISO week number.

verifiedBusiness Days Skipping

Optionally skip Saturdays and Sundays to find strict work project deadlines.

verifiedComprehensive Calendar Metadata

Surfaces day of week, day of year, and ISO week number.

Standard JavaScript Date arithmetic rolls over into the subsequent month if the target month has fewer days.

Date & Time

Calculate exact age in years, months, days, total days lived, and countdown days until your next birthday.

Calculate the exact duration between two dates in total days, full weeks, months, years, and working business days.

Calculate working business days and total working hours between two dates, excluding weekends and custom holidays.

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