On the official game blog, the Pokemon Go team says:
With Valentine's Day just around the corner, we couldn't think of a sweeter time to double the amount of Candy you'll earn every time you catch, hatch, and transfer Pokémon. Your Buddy Pokémon is also getting into the Valentine's Day spirit and will find Candy twice as fast!
Candy is always dandy, but the real draw for Pokemon collectors is going to be more frequently spotted pink-colored creatures.
Throughout the celebration, you'll notice that Chansey, Clefable, and many other adorable pink Pokémon will be encountered more frequently in the wild.
It's not the most epic update in the world, but at least you'll have more than the 24 hours that officially constitute Valentine's Day to collect these extras. The Pokemon Go Valentine's Day Celebration runs from today through Feb. 15.