The Cash App weekly limit reset doesn't occur at a certain time.
It's determined by when your Cash App account was created and when you surpass your limit.
For example, if you opened a Cash App account on the 11th of a month, your one week will end on the 18th of that month.
The key is spending your $7,500 (or $250 for unverified users) in a span of 7 days.