The heart on the calendar

She seemed excited for the whole week. He never saw her with that bright, sunshine-liked smile on her face. He remembered one day she checked on the Internet for some kind of recipes. As the matter of fact, John's girl also came around and they spent a whole day in the kitchen mumbling about some weird stuff that he never bothered to find out. But, there was a big red heart on their calendar on the 14th of February. And she did tell him she like roses. Very much.

Why do people have to invent such day as Valentine's Day?