How do I get the week ending date for a specific day?

Assuming tdate contains the day you'd like to convert:

@If(tdate != ""; @Adjust(tdate; 0; 0; @Modulo(8 - @Weekday(tdate); 7); 0; 0; 0); tdate)

Applies to Notes Versions: 3, 4, 4.5, 4.6, 5