But this story is about 45 Philadelphia couples who do know that and they're marking the occasion in a very special way.
At City Hall today, there was snow on the ground, but love in the air as a dozen judges joined some 45 couples in matrimony.
For Kathy and Chris, this City Hall wedding was meant to keep bad luck away from their marriage and their big wedding, which is set for October 10th.
"On Sunday, it's also Chinese New Year and it will be the Year of the Tiger and my mother says it's bad luck to get married or start a new business during the Year of the Tiger," Kathy Tsai said.
For Paul and Rosana, who're from Russia, but studying here in Philadelphia, it was a chance for a Valentine's Day wedding in what for them is an exotic location.
And for Herbert and Katie, who've been together for 12 years, it was a matter of finally doing everything right.
"He kept telling me we were getting married and then he finally asked me," Katie Duncan said.
Some of these couples are planning receptions right after these ceremonies; others are waiting for the summer.
One thing is for sure. They hope their love declared today will last through all the seasons.