Work with the example
Which Monday and Sunday surround the supplied observation date? B5 starts on Sunday 2026-10-18. The workbook explicitly uses WEEKDAY type 2, where Monday=1 and Sunday=7. This is a seven-day heading, not an ISO week-number rule.
| Cell | Baseline |
|---|---|
| E5 weekday index | 7 |
| D5 Monday | 2026-10-12 |
| D6 Sunday | 2026-10-18 |
Edit the working cells
D5 uses guarded B5-WEEKDAY(B5;2)+1; D6 adds 6. The seven displayed dates link to that Monday. Change B5 to October 19: Monday 19 through Sunday 25. A fresh January 1,2027 belongs to December 28,2026 through January 3,2027. Clear B5 and the working cells show Date missing.
Check the failure case
Omitting the type changes the weekday numbering. Treating a default Sunday 1 as though Monday were 1 gives the wrong start. Crossing a year does not require replacing the date with a text year label.
Is January 1 necessarily the first day of its Monday-start week?
Show the worked answer
No. In this example the week starts on December 28 of the preceding year.