Twins born in California have different birthdays in different years.

The first twin, a baby boy named Joaquin, was born at 11:58 p.m. local time Sunday. Eighteen minutes later, at 12:16 a.m. Monday, his little sister Aitana entered the world.

He was 5 pounds, 9 ounces and 18 inches long. She was a little smaller at 4 pounds, 10 ounces and 16 inches long and was delivered by caesarean section, KERO reported.

They made their debut at the Delano Regional Medical Center as the last baby of 2017 and the first of 2018.

The new parents said their New Year’s babies were born about a month early after being originally due on Jan. 27 but they had a C-section scheduled for Jan. 10, KERO reported.

The family has three other girls between the ages of 6 and 18 years old, KERO reported.

RELATED: Here’s how one flight took off in 2018 and landed in 2017