Date & Time
Get Monday of the week from any date (weekly cohort grouping)
Roll daily timestamps back to the Monday (or Sunday) starting their week using Date - WEEKDAY(Date, 2) + 1.
Bucket daily transactions by week-starting Monday
A week-start date provides an explicit grouping key across year boundaries. Week numbers alone can be ambiguous without a year and a clearly selected week-number convention.
WEEKDAY(date, 2) numbers Monday = 1 through Sunday = 7. Subtracting WEEKDAY(date, 2) - 1 steps Thursday back 3 days to Monday while leaving Monday itself unchanged (1 - 1 = 0).
The displayed examples return text labels. For numeric grouping keys use INT(date)-WEEKDAY(date,2)+1 without TEXT. Sunday-start is a reporting choice rather than a rule for every US organization.
| TxDate (A) | Day of Week | ISO Monday Start | US Sunday Start |
|---|---|---|---|
| 2026-04-16 (Thu) | ISO 4 | 2026-04-13 | 2026-04-12 |
| 2026-04-13 (Mon) | ISO 1 | 2026-04-13 | 2026-04-12 |
| 2026-05-02 (Sat) | ISO 6 | 2026-04-27 | 2026-04-26 |
Monday-start and Sunday-start week anchors
Change return_type from 2 to 1 inside WEEKDAY(A2, 1) when your reporting week begins on Sunday.
=TEXT(INT(A2) - WEEKDAY(A2, 2) + 1, "yyyy-mm-dd")US Sunday-start week formula
Thursday April 16, 2026 maps to Monday 2026-04-13 (ISO) or Sunday 2026-04-12 (US).
=TEXT(INT(A2) - WEEKDAY(A2, 1) + 1, "yyyy-mm-dd")Try the example
Use the original values or change them to test your understanding.