Date & Time
Get the first day of the month (current, previous, or next month)
Anchor any date to the 1st of its month—or shift cleanly to prior or upcoming months—with EOMONTH(date, n) + 1.
Why EOMONTH(date, -1) + 1 scales across every month offset
EOMONTH(A2, -1) steps back to the final day of the previous month; adding 1 day lands on the 1st of the current month. Changing -1 to -2 lands on the 1st of the prior month, and 0 lands on the 1st of the next month—rolling across December/January year boundaries automatically.
For the current month only, INT(A2) - DAY(A2) + 1 also subtracts the day-of-month offset directly.
TEXT returns a display label. Omit TEXT to retain a numeric date for arithmetic and format that cell as a date. INT removes a timestamp’s fractional time in the direct-subtraction version.
| Input Date (A) | 1st of Prior Month | 1st of Current Month | 1st of Next Month |
|---|---|---|---|
| 2026-04-19 | 2026-03-01 | 2026-04-01 | 2026-05-01 |
| 2026-12-15 | 2026-11-01 | 2026-12-01 | 2027-01-01 |
Current, prior, and next month start formulas
From 2026-04-19, EOMONTH(A2, -1) + 1 produces 2026-04-01 and EOMONTH(A2, -2) + 1 produces 2026-03-01.
=TEXT(EOMONTH(A2, -1) + 1, "yyyy-mm-dd")Direct day-subtraction alternative
INT(A2) - DAY(A2) + 1 strips any fractional clock time and lands on day 1 of the same month.
=TEXT(INT(A2) - DAY(A2) + 1, "yyyy-mm-dd")Try the example
Use the original values or change them to test your understanding.