A rest window is a block of hours when the account takes no new trades. You set it on the account's Your limits page.
A window is a time and a time zone
"10pm" is not a time until you say where. A rest window is a clock time plus a time zone. When you move the window, it is saved in the time zone you are reading in. This matters: a window saved in one time zone and read in another is off by the hours between them.
In a strategy you build, the rest window asks for three things: the time zone, the start, and how long it lasts. It will not save until all three are filled in. A strategy saved without them shows the window it runs with written in: 10pm London, for eight hours.
Checking your rest hours
Rather than guessing a window, there is a scan. It queues real backtests over the last thirty days, with and without each candidate window, at the same risk anchor the pipeline uses, and ranks what each one would have cost.
Every row is a real backtest with that window switched on, run by the same engine that runs your live trading. Results are emailed, so you can start it and leave the page.
The scan runs in the same zone an apply writes in, so the window that gets saved is the window that was measured.
Reading the result
The table gives you the figures. Which window you want is your call, and the tool names no winner.
Where you see it working
While a rest window is on, the Activity page's Everything else tab records each refused entry as your rest window being on.
You need a strategy on the account first
The scan measures what a rest window would have cost your strategy, so it needs to know which one that is. On an account with no strategy yet, the scan will not start, and it says so. Pick a strategy on the Running now tab of the Strategies page, and the scan is available.
What can go wrong
If your own window is saved in a different time zone from the scan, it is left out of the table rather than shown in the wrong place. A row labelled 10pm that was measured at 3pm would be worse than no row.