AWS Athena: syntax for grouping data for week ending on a Saturday

I'm having some issues with the Presto syntax in grouping data by separate weeks, ending on Saturdays. I have this field called "timestamp," and I've been using the the following to group by weeks. However, I noticed that date_truncs weeks ending on a Monday and using a date_add doesn't necessary group all rows correctly. select date_add('day', 5, date_trunc('week', date(substr(timestamp, 1, 10)))) as week_ending Any suggestions on how I can group weeks ending on Saturdays? Thanks!