Same day is the ordinary case here. Most of what this service does happens inside the same twenty-four hours as the message that started it, and a good share of it inside the same two hours.
The arithmetic is short. Confirmation comes first, by message. Travel usually takes forty to sixty minutes across the centre. So the gap between sending an address and hearing a knock is usually a little under an hour, and there is no version of the process that is meaningfully faster than that.
What more notice actually buys
Not speed. Forty minutes is forty minutes whether you booked it at noon for 14:00 or wrote the message at 02:50 for right now.
Not price either. The rates table on each profile does not move for lead time, and it does not move for the hour of day. An hour booked for a Tuesday afternoon costs to the cent what an hour at 04:00 on a Saturday does.
What notice buys is choice. Three kinds of it.
The first is a particular therapist. There are forty-five on the roster and they do not all work the same hours. If you have read the profiles and settled on a name, asking earlier in the evening rather than at midnight is the difference between that name and a different one.
The second is two therapists. A four-hand booking for one guest, billed at double the hour, needs two diaries to line up instead of one, which is straightforwardly harder to do at short notice than at three hours' notice. Same for the longer end of the ladder. Three hours, or an eight-hour overnight, means holding a large block open, and a large block is easier to find before it has been broken up by shorter bookings.
The third is a specific format. The service pages are not interchangeable, and not every therapist offers every one of them. A same-day booking with no preference attached is almost always possible. A same-day booking with three conditions attached is a narrower ask.
What same day looks like in practice
A message with an address, a time and a duration. A confirmation with a name and an arrival window, in the same thread. Then the window.
"Now" is a valid start time. So is "in an hour", which is often the better one, because it gives you time to finish whatever you are doing rather than spending the arrival window rushing. There is no advantage to compressing it.
If you want a specific hour later the same day, say the hour rather than saying later. "Tonight" is not a time. "23:00" is, and it gets held.
The edges of same day
Schiphol airport hotels are the one case that needs more than the usual notice. Those sit outside the forty-to-sixty-minute figure and are arranged on enquiry rather than booked on the spot.
Everything inside the ring behaves the same as everything else inside the ring. Leidseplein at 23:00 and a quiet street in the north of the Jordaan at 05:00 are the same forty minutes and the same price. There is no zone where same day stops working.
Booking tomorrow instead
Advance bookings are held the same way as same-day ones, with the same written confirmation. Nothing is gained by booking a week out and nothing is lost by it either, beyond the small chance that plans change and the booking has to move. That is easy to do, as long as it is done before the arrival window opens.
The short version: if the thought has occurred to you tonight, tonight is available. The hours the therapists choose cover the whole night, so a late message usually finds a name.