Dates are numbers

Under the formatting, every date in Sheets is a whole number: the count of days since December 30, 1899. March 9, 2026 is 46090. That's why date math is just arithmetic:

• Days between: =C2-B2. Later date minus earlier date.
• A week from now: =B2+7.
• Whole months or years between: =DATEDIF(B2, C2, "M") or "Y". Good for tenure and customer age.

Two functions handle the calendar for you:

• EOMONTH(date, months) returns the last day of a month. EOMONTH(B2, 0) is the end of this month, EOMONTH(B2, 1) the end of next month. EOMONTH(B2, -1)+1 is the first day of this month.
• NETWORKDAYS(start, end, holidays) counts Monday-to-Friday days, both ends included, and skips any dates in a holidays range.

If a result shows as a date when you wanted a count, or a number when you wanted a date, the math is fine. Change the cell's format under Format › Number.

Watch out for dates typed as text, often from CSV exports: they sit on the left of the cell and break every formula. DATEVALUE converts them.