When the next update is sent to the channel the inventory will be updated, this is not an instant update. You can manually send an update from the channel connection page.
If you need to set availability closed at a certain time of day most OTA's have their own settings for this type of rule and it can be set at the OTA.
For example, Airbnb has a setting called "Advance Notice (hours)" which sets the number of hours before midnight you want to stop same day bookings.
Other OTA's may have similar settings internally that they can set for you, please check with the specific OTA.
== Booking Engine ==