"Stop being so cheerful, Mad-Eye, he'll think we're not taking this seriously."
-- Nymphadora Tonks in response to Mad-Eye's dire warnings about imminent death (OP3)
Tonks arrives with the other members of the Guard in Privet Drive and remarks about the “unnatural” cleanliness of the Dursley’s house. When the group travels from Little Whinging to Grimmauld Place, Tonks flies with Harry’s trunk suspended under her broom.
Since the sun set at 8:42 pm on that day and they left after dark, we can assume that the flight took place around 9:30 pm.