When It Actually Is
National Girlfriends Day is August 1, every year, observed mostly in the United States and increasingly everywhere the internet reaches. It is a girlfriend appreciation day in both senses: people mark it with their partners and with their closest friends.
Its origins are genuinely murky. Several people are credited with inventing it depending on which page you read, there is no governing body, and nobody registers these things anyway. The date stuck the way internet dates stick: enough people agreed, and now it is August 1.
If you are looking for the matching date on the other side of the calendar, National Boyfriends Day is October 3, equally unofficial, equally worth keeping. Mark that one in her calendar while you are setting this one in yours, and you have covered the year's two made-up-but-charming checkpoints.
The only real rule: the day works if you do something, and it evaporates if you do not. There is no wrong bigger than letting it pass silently.