EXTRACT(WEEK from <date>) functionality is very using in BigQuery for quickly grouping actions into dates, but the default week begins on Sunday.
For us, it makes more sense for our weeks to begin on Mondays. To do that you can do:
EXTRACT(WEEK(<WEEKDAY>) FROM <DATE>) as Week
DATE_TRUNC(<DATE>,WEEK), you can do:
DATE_TRUNC(<DATE>,WEEK(<WEEKDAY>) as week_commencing
<DATE>is the date column you’re transforming