From Longman Dictionary of Contemporary Englishit’s not somebody’s dayit’s not somebody’s dayUNLUCKYused when several unpleasant things have happened to someone in one day It wasn’t Chris’s day – he overslept and then his car broke down. → day
Examples from the Corpus
it’s not somebody’s day• It's not every day a young woman pulls a gun on a burglar.• After all, it's not every day you win an arena referendum and a game against the defending champion Lakers.• Well, it's not every day, is it? 