Along with British society, the royal family has been gradually modernizing its attitudes to birth and parenting. William's father, Prince Charles, was present at the birth of his two sons, who were born in a hospital rather than a palace - both breaks from royal tradition. But William is the first senior royal to receive statutory paternity leave, which was introduced in Britain in 2003.
Some family campaigners say William, a Royal Air Force search-and-rescue helicopter pilot, is setting a good example in a country where until recently new fathers have taken little time off.
But others say two weeks is not enough, and argue social and economic pressures still discourage fathers from spending time looking after their newborns.
"There is an element that employers - and men themselves - are thinking of them as the ones who earn the money and stick in that role when children come along," said Jeremy Davies of the Fatherhood Institute think tank. "It can be quite difficult to set yourself apart from that."
Under British law, William is entitled to two weeks off at a flat pay rate of just under 137 pounds ($206) a week. He's lucky - the military is among employers that pay more, and he will receive his full salary for the fortnight.
The government says two-thirds of new fathers take some paternity leave, but less than half take the full two weeks. Some are ineligible because they are self-employed or haven't been at a job for at least six months. Others just can't afford it.
Mothers, who receive the bulk of parental leave, can take up to a year off, though only 39 weeks of it is paid, and not at full salary.
The rules are changing. Under recent changes, new fathers can take up to six months leave by using up some of the year of a partner who has returned to work.
But few do. Elizabeth Gardiner of campaign group Working Families said that in the first year the flexible leave was offered, only 1,650 men in Britain took it.
She said the solution is to set aside some time off for fathers only - a practice in Scandinavia known as "daddy months."
"If you really want fathers to take up leave you have to earmark it for them and you have to pay it properly," she said.
That's what they do in Sweden, where new parents can take 16 months' paid leave, divided between the parents as they like. Two months can only be taken by the mother and two months by the father - if not, the time cannot be transferred to the partner and is forfeited.
As an incentive, it works - In 2000, Swedish men took out only 12.4 percent of parental leave; by 2010 their share had nearly doubled to 23.1 percent, according to government statistics.
At the other end of the scale is the United States, where there is no government-subsidised nationwide paid paternity leave, though some companies and a few states including California offer it. Many companies and the public sector offer unpaid leave to new fathers.
Britain is moving to offer fathers more time. Under legislation currently before Parliament, from 2015 parents will be able to split the 50 weeks of paid leave as they like.
Changing attitudes may be harder than changing the law. A recent study by the Rotman School of Management at the University of Toronto found that men who take on caregiving duties at home receive more abuse at work than men who stick to conventional gender roles.
"It was a pretty powerful result," said Jennifer Berdahl, professor of organizational behavior at the Rotman School. "Men who did relatively more caregiving at home experienced a lot more 'not man enough' harassment and teasing that threatens their status in the workplace."
Prime Minister David Cameron took two weeks' leave when his daughter Florence was born in 2010, and it drew comment - some approving, some critical of a national leader stepping back for 14 days to look after a baby.
Jeremy Davies of the Fatherhood Institute said William was setting a good example - up to a point.
"What would be fantastic would be to see Prince William to take some time where he was the primary carer at some time during the first year," Davies said. "That's the stuff that leads to a really strong relationship with the child."