At 3 a.m. the calendar is open just the same. Shift workers, people who study after their day job, anyone whose clock runs the other way round: coworking slots don't close at office hours.
If you work nights or shifts, everything tends to be closed when you're awake: shops, offices, and the fixed appointments that would help you get started. Here a session opens every quarter hour, all day and all night: there's no “after hours” slot, just slots.
When it's 3 a.m. in Europe, it's evening somewhere else, so a night slot isn't limited to people in your time zone. Night slots are still quieter than daytime ones, and sometimes a slot stays empty for a while before someone joins: the first question below says what happens then.
In slots with fewer people it's more likely that nobody shows up for a while. The session starts anyway: for the first 5 minutes we look for someone while you work. If nobody arrives, you choose: carry on with a virtual companion, and if you stay until the end the session counts in full, look for a person in the next quarter hour, or leave.
No, you just book the slot you need: there are no time categories to declare.
Yes, the timer with weighted hours is always available, even without a coworking session.