Day-Lewis' kids thought he was a builder
The 55-year-old is nominated in the best actor category for the 85th Academy Awards for his portrayal of US President Abraham Lincoln.
Day-Lewis even quit acting in the 1990s to become a cobbler, before returning to the big screen in the 2002 film "Gangs of New York".
He says his acting career was such a mystery to his sons that his second child Ronan presumed he worked in construction.
"They didn't even know what I was doing until a couple of years ago.
In fact, my 14-year-old boy was asked what I did and he said, 'I think he's in construction'," dailymirror.co.uk quoted him as saying.