Any way to filter by week number?
Here's a trick: create a new date format by navigating to Admin > Configuration > Regional and Language > Date and Time and clicking on the Formats tab (admin/config/regional/date-time/formats).

Set it to W (that's uppercase W), and it will give you week number, which you can use with any date.

That way you can include the date field directly in views, set the W filter and use the aggregation, filter, etc without any additional coding.