"Justin Trudeau was born on 25 December 1971. By means of a rough estimate, we note that a 2013 study published in the journal Human Reproduction used data from 130 pregnancies to investigate the range of different pregnancy lengths from conception to birth (gestation) and reported a range of from 247 to 284 days: It is extremely unlikely that Justin’s birth fell outside of that gestational range, meaning that Castro and Margaret Trudeau would have to have conceived their secret love-child between March 16th and April 22nd, 1971. It should be noted that Margaret and Pierre Trudeau were secretly wed on March 4th, 1971, and honeymooned until March 8th. When they returned home, Margaret moved in with the prime minister for the first time. If ever there were a time to make a baby and have it be born in late December, it would have been then, as hinted at in a Harper’s Bazaar profile of Margaret: "Margaret moved into the prime minister’s official residence, at 24 Sussex Drive in Ottawa, and gave birth to Justin just 10 months after the wedding, on Christmas Day in 1971.""