Dates and reporting
DAYS function: count elapsed calendar days between two dates
Calculate exact calendar days between an issue date and settlement date, remember that end_date comes first, and interpret negative results for early settlements.
Invoice settlement vs due-date variance
An invoice issued on 1 April 2026 (serial 46113 in B2) is due on 15 April 2026 (serial 46127 in C2) and settled on 19 April 2026 (serial 46131 in D2).
| Invoice (A) | Issued (B) | Due (C) | Settled (D) |
|---|---|---|---|
| INV-71 | 2026-04-01 (46113) | 2026-04-15 (46127) | 2026-04-19 (46131) |
Put end_date first and start_date second
Unlike DATEDIF or NETWORKDAYS (which start with start_date), DAYS(end_date, start_date) subtracts the second date from the first: =DAYS(D2, B2) computes 46131 - 46113 = 18 elapsed calendar days.
Comparing Settled against Due—=DAYS(D2, C2)—returns 4 days late.
=DAYS(D2,B2)Early payments return negative days
Unlike DATEDIF (which errors with #NUM! when dates are reversed), DAYS simply returns a negative number. Change D2 to 12 April 2026 (serial 46124) and =DAYS(D2, C2) evaluates to -3, showing the invoice was paid 3 days early.
=DAYS(D2,C2)Try the example
Use the original values or change them to test your understanding.