People are scratching their heads after a US hospital posted a riddle about the age of twin boys born in November.

The twins were born 31 minutes apart, yet the second born is older than the first - at least on paper, accoridng to The Sun.

The confusing occurence can be easily explained.

Samuel Peterson was born on Sunday, November 6, 2016 at 1.39am.

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He was followed by his twin brother Ronan 31 minutes later at what would have been 2.10am.

But at 2am, Daylight Savings ended for the year making it 1.10am according to the official record, meaning Ronan is older than his brother.

Cape Cod Healthcare posted about the event on facebook, and shared a photo of the boys with mum Emily and dad Seth, from West Barnstable, Massachusetts.

Realising how close his sons were going to be born to midnight, Seth, 45, told One Cape Health News: "I said, they're either going to be born on two different days, or the time change may come into play."

Emily, 32, said she heard the nurses talking before seeing the hands moving backwards on the clock in the birthing room.

She admitted: "I thought my brain was playing tricks on me!"

Deb Totten, a maternity nurse at the Cape Cod Hospital, said: "It's the first time I have ever seen this in over 40 years of nursing."