Add or Subtract From a Date

How month-end dates are handled

Adding months keeps the same day of the month. When that day does not exist, the result moves to the last day of the month, the same rule used by Excel’s EDATE and many billing systems:

One consequence: adding one month and then subtracting one month does not always return you to the start date. January 31 plus a month is February 28, and February 28 minus a month is January 28.

Common uses

• Payment terms: an invoice dated today with Net 30 terms is due Thursday, November 5, 2026. See also 30 days from today.
• Notice periods: subtract days or weeks from a leaving date to find when to hand in notice.
• Pregnancy due dates: doctors traditionally add 280 days (40 weeks) to the first day of the last period for an estimate. Always confirm with your healthcare provider.
• Warranties, returns and trials: add 30 days, 90 days or 1 year to a purchase or sign-up date.
• Contracts and leases: add months rather than days when the contract is written in months.

Adding dates in Excel and Google Sheets

• Add days: =A2+30 (or =A2-30 to subtract).
• Add months: =EDATE(A2,3). Use a negative number to subtract.
• Add business days: =WORKDAY(A2,10,H2:H12), where H2:H12 lists holidays to skip.