Azaria Heyde Hernandez-Santos was born at Alta Bates Summit Medical Center in Berkeley at 12:07 a.m., hospital spokeswoman Carolyn Kemp said.
Brandon Lin was also born at 12:07 a.m., at ValleyCare Medical Center in Pleasanton, said Denise Bouillerce, director of marketing for that hospital.
Azaria, weighing in at 4 pounds 5 ounces, was born to Stephanie Hernandez. She was born prematurely and her original due date was on Valentine's Day, Kemp said.
"She's a beautiful little baby," Kemp said. "She's happy and healthy."
Brandon, who weighs 6 pounds 14 ounces, was born to Su-lyn and Peter Lin as crowds around the Bay Area celebrated the new year.
"It will be nice a few years down the road when we can tell him he was one of the first babies born in 2011 and that his birth was accompanied by fireworks," Su-Lyn Lin said.