Meet the twins born in separate years after mother's premature New Year's Eve labour

Joaquin (left) was born at 11.58pm on New Year's Eve 2017; Aitana (right) was born 12.16am on New Year's Day 2018 in Delano, California. Photo / Delano Regional Medical Center

These twins were born just 20 minutes apart - but in different years, months and days.

Joaquin and Aitana de Jesus Ontiveros were both due to arrive January 27, 2018.

But at 7pm on New Year's Eve, their mother Maria went into labour prematurely, and the babies arrived naturally either side of midnight in California's Delano Regional Medical Center.

Joaquin, was born weighing 5lbs 9oz at 11.58pm on December 31, 2017, while his younger twin sister Aitana arrived at 12.16am on January 1, 2018, weighing 4lbs 10.8oz, according to the Daily Mail.

It means that while they share everything from genes to mealtimes, they will not share a birthday, birth month, or even a birth year.

Due to the unlikely timing, Maria and her husband Joaquin, both farm labourers who have three other daughters together, will also take home more than US$3,000 ($4,216) worth of baby supplies, donated to the hospital by local community groups.

Speaking to Daily Mail Online on Monday afternoon, a spokesman said both babies and their mother are healthy and ready to go home to Earlimart, a small neighborhood between Fresno and Santa Barbara, after an emotional night.

"It was definitely a surprise! The whole family feels humbled and blessed and excited," the spokesman said.

"When they realised they were going to be in the hospital over New Year's Eve, the family planned to celebrate at midnight in the break room.

"But then it turned out Maria was in labour, which was a surprise."

Their birth dates are incredibly uncommon, but 12 months ago four such twin births were recorded in the US - in Georgia, Utah, Arizona and San Diego in California.

The year before, there was just one, also in San Diego.