The birthday of Blake Lively and Ryan Reynolds' daughter James' has remained a burning mystery to the general public — until now.Today, Reynolds let the cat out of the bag in a tweet celebrating the 1-year-old's special day. Reynolds and Lively have spoken openly about parenthood and James over the past year, but neither of them had officially revealed the exact date that they became proud parents."Happy birthday to my baby girl! Sad I lost my virginity. But thankful I have a daughter," Reynolds tweeted on Wednesday. The message reveals that December 16, 2015 marks the first anniversary of James' existence.Reynolds' tweet also shows that fatherhood has only bolstered his sense of humor. This isn't the first time Reynolds has offered a lighthearted remark about being a parent. On Friday, Reynolds tweeted , "Love writing nursery rhymes for my daughter. Her favorites are, 'Sunshine-Cuddle-Time!' and 'Everyone You Know Will Eventually Die.'"