# WEEK diff between Saturday and Sunday, counts as 1 because of WEEK (Sunday) crossing 
bq> SELECT DATE_DIFF('2026-01-04', '2026-01-03', WEEK);
1

# ISOWEEK diff counts as 0 because of ISOWEEK (Monday) is not crossed 
bq> SELECT DATE_DIFF('2026-01-04', '2026-01-03', WEEK);
0

# Monday crossing does NOT count: 
D SELECT DATE_DIFF('WEEK', '2026-01-03'::DATE, '2026-01-06'::DATE) AS num_weeks;
┌───────────┐
│ num_weeks │
│   int64   │
├───────────┤
│     0     │
└───────────┘

# Count increases only when day delta exceeds >= 7:
D SELECT DATE_DIFF('WEEK', '2026-01-03'::DATE, '2026-01-10'::DATE) AS num_weeks;
┌───────────┐
│ num_weeks │
│   int64   │
├───────────┤
│     1     │
└───────────┘