Excel Date Functions

Excel stores every date as a serial number (days since January 1, 1900), which means date math is just arithmetic plus a handful of functions: TODAY for the current date, EOMONTH for month ends, NETWORKDAYS for business days, DATEDIF for ages, and EDATE for shifting by months.

How Do Excel Date Serial Numbers Work?

A date is an integer count of days — January 1, 2026 is serial 46023 — so subtracting two dates gives days between them, and adding 7 to a date gives next week.

=B2-A2        ' Days between two dates: plain subtraction
=A2+7         ' Same day next week
=TEXT(A2,"yyyy-mm-dd")   ' Format a serial as text

If a formula shows a number like 46023 instead of a date, the value is fine — only the cell format is wrong. Apply a date format.

What Do TODAY and EDATE Do?

TODAY() returns the current date and recalculates every day the file opens; EDATE shifts a date by whole months, handling month lengths for you.

=TODAY()             ' 2026-07-31 (recalculates daily)
=EDATE(A2, 3)        ' 3 months after A2
=EDATE(A2, -12)      ' 1 year before A2
=EDATE("2026-01-31", 1)   ' 2026-02-28: clamps to real month end

How Do You Get the Month End With EOMONTH?

EOMONTH returns the last day of the month a given number of months away, which makes it the standard tool for reporting periods and due dates.

=EOMONTH(TODAY(), 0)      ' Last day of this month
=EOMONTH(TODAY(), -1)     ' Last day of last month
=EOMONTH(TODAY(), -1)+1   ' FIRST day of this month
=EOMONTH(A2, 1)           ' Invoice due: end of next month

How Do You Count Business Days With NETWORKDAYS?

NETWORKDAYS counts weekdays between two dates inclusive, with an optional range of holiday dates to skip.

=NETWORKDAYS(A2, B2)             ' Weekdays from A2 to B2
=NETWORKDAYS(A2, B2, $H$2:$H$10) ' Excluding listed holidays
=WORKDAY(A2, 10, $H$2:$H$10)     ' Date 10 business days AFTER A2

What Is DATEDIF and Why Is It Hidden?

DATEDIF returns the gap between two dates in complete years, months, or days — it's undocumented in the function wizard but works in every Excel version and is the cleanest way to compute ages and tenure.

=DATEDIF(A2, TODAY(), "y")   ' Complete years (age, tenure)
=DATEDIF(A2, TODAY(), "m")   ' Complete months
=DATEDIF(A2, TODAY(), "ym")  ' Months left over after years
' "34 years, 5 months":
=DATEDIF(A2,TODAY(),"y")&" years, "&DATEDIF(A2,TODAY(),"ym")&" months"

Common Pitfalls

• Text that looks like a date: imported "dates" stored as text won't sort or subtract. Use =DATEVALUE(A2) or check with =ISNUMBER(A2).
• TODAY() is volatile: it recalculates constantly. Never use it for a fixed "date entered" stamp — press Ctrl+; instead.
• DATEDIF argument order: start date must come first or you get #NUM!.
• NETWORKDAYS counts both endpoints: Monday to Friday of the same week returns 5, not 4.
• Adding 30 for "next month": use EDATE(A2,1), not A2+30 — months aren't all 30 days.