No, silly. Not your literal window. That might be dangerous! You know when you're most productive. You might be a morning person, or an evening person. The concept of flex time can be easily adopted when you're working on a distributed team. Bonus points if your team prioritized async communication and is spread across time zones. Identify when you're most productive and try your best to safeguard that time for deep work. You don't necessarily have to stick to the 9-5 schedule if you prefer starting at 6 a.m. or finishing at 11 p.m.