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Tom Becker 3 min readFormulas2028 is a leap year, so February ends on the 29th.
Dates without tears: due dates, month ends and working days
Dates are just numbers in Excel. Once that clicks, due dates, month-end reports and working-day counts become simple arithmetic.
Tom BeckerDates without tears
Dates are numbers
Excel stores a date as the number of days since 1 January 1900, so 12 Nov 2026 is 46338. That’s why you can add days with a plain +.
Invoice due dates
D2fx=B2+C2
A
B
C
D
1
Invoice
Issued
Terms
Due
2
INV-01
12 Nov 2026
30
12 Dec 2026
3
INV-02
3 Nov 2026
14
17 Nov 2026
4
INV-03
20 Oct 2026
45
4 Dec 2026
Month ends with EOMONTH
EOMONTH(date, months) returns the last day of a month: 0 for this month, 1 for next, -1 for last. It handles February and leap years for you.
EOMONTH
B2fx=EOMONTH(A2,0)
A
B
C
1
Date
Month end
Next month end
2
12 Nov 2026
30 Nov 2026
31 Dec 2026
3
3 Feb 2026
28 Feb 2026
31 Mar 2026
4
15 Feb 2028
29 Feb 2028
31 Mar 2028
Count and add working days
| Formula | Result | Why |
|---|---|---|
| =NETWORKDAYS("2 Nov 2026","30 Nov 2026") | 21 | Weekdays, both ends included |
| =NETWORKDAYS("2 Nov 2026","30 Nov 2026",H2:H3) | 20 | Minus a holiday on 26 Nov |
| =WORKDAY("12 Nov 2026",10) | 26 Nov 2026 | 10 working days later |
| =DATEDIF("15 Mar 2019","12 Nov 2026","y") | 7 | Complete years between dates |
| =DATEDIF("15 Mar 2019","12 Nov 2026","ym") | 7 | Remaining complete months |
Try it in a live spreadsheet
Practise these formulas in interactive lessons with instant grading.
Tom Becker
Financial analyst at FluentExcel
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