Sydney Airport opening times are:
T1 International terminal
T1 International is open every day from 2:30AM to 11:00PM (02:30 to 23:00).
Customs opens for departures passenger processing at 4:00AM daily (04:00).
T2 and T3 Domestic terminal
T2 Domestic and the T3 Domestic terminal open every day from 4:00AM to 11:00PM (04:00 to 23:00).
There is a government mandated curfew operating at Sydney Airport between 11:00pm and 6:00am. For security reasons, the terminal is closed to the public overnight. During the times the airport is closed, there are a range of accommodation options on and off-airport from budget hotels to five-star establishments which may be booked online.
There are airport hotels located nearby Sydney Airport for travellers in transit.