Although apparently, it seems that it is not possible to group dates by weeks,
you can choose the grouping according to days and change the number of days to 7.
Please note that the grouping will be done every 7 days,
starting from the first date in your database,
so there may be a situation where the grouping will be done from Wednesday to the following Tuesday.
If you want the grouping to always start on Sunday,
check the date of the first Sunday before the first date in the database and change the start date,
as shown in the following example: