Gilderoy Lockhart wrote in one of his books about how he defeated a werewolf that was terrorizing the folks of Wagga Wagga in Australia. He didn’t actually accomplish this heroic feat, of course, but rather learned about some other wizard who had done so, modified their memory to forget about it, and claimed the actions as his own (CS10).
When did Lockhart perform all his heroic feats, such as the battle with the Wagga Wagga Werewolf? According to Pottermore, he created an image of himself to project into the sky copying the Dark Mark which Death Eaters used in the 1970s, so we can place his time at Hogwarts to be in that decade. Pottermore also says that Lockhart became famous for his supposed heroic deeds in the decade after leaving Hogwarts, which could place the Wagga Wagga Werewolf incident as happening in the 1980s. We'll use that "best guess" logic to place this incident in the early 1980s.