"Mum, d'you honestly think You-Know-Who's going to be hiding behind a bookshelf in Flourish and Blotts?"
-- Ron Weasley sniggered, in response to an over-cautious Mrs. Weasley (HBP6)
There they meet up with Hagrid, have a run-in with Draco and Narcissa Malfoy in Madam Malkin’s, visit Weasleys’ Wizard Wheezes, and follow Draco to Borgin and Burkes, where they overhear him threatening Mr. Borgin.
This happened the Saturday following Harry's birthday. According to the calendar used by the rest of the book, this day would be August 3.