If you are referring to the Time Card Template that comes with FileMaker, STOP. It is based on a design that goes back almost two decades before FMP was relational. It uses repeating fields to store data, which is completely against the relational model that is now functional in FMP (really since version 3)
Several posts by PhilModJunk on this forum contain a link to a very basic Invoice file. A time keeping program in its simplest form is modeled very similarly to it. Employees are the Contacts or Customers, Time Cards are the Invoice and the Line Items are Days, but instead of products and prices you would have fields for Start_Time, End_Time and Total_Time. I like using timestamps for the start and end because any hours over midnight will still calculate correctly. The Total_Time for the day is just the End_Time - Start_Time, results formatted as time. There are functions available online that will convert this into a decimal.
You can isolate the Days by creating a calculated field in Days that get the Week of the Year from the Start_Date and then with a global field in Invoices make multi-key relation to the Week number and Employee ID and get a sum of the total hours worked for the week much like the total of an invoice from line items.
For your original question, with the above model you can do a find by month and then sort by the week which would be very easy to do in a sub-summary report or just expand the portal filtering a bit.
If you look at the Time Billing Template you will see what I am talking about, but even that fails to separate the Employees from the Time records.
Any questions, just ask, but I will be in and out this weekend so it may be a while before I can respond.