Partners for nearly a decade, Sarah Keith and Emma Powell are moving next month from their native England to New York. But first, they have an important piece of business to take care of: their wedding.

“We’re quite calm about it,” Powell said Friday as she strolled the coastal streets of Brighton with 24 hours to go before “I do” time. “We’re not bridezillas.”

England, too, has been quite calm about their wedding, even though it marks the sort of transformational moment that has both cheered and horrified people worldwide in recent years.

With the stroke of midnight, same-sex couples were, for the first time, permitted to marry in England and Wales, and many did in middle-of-the-night celebrations. The weddings united same-sex partners who have for a decade been allowed to form civil partnerships, but until now have been prohibited from tying the knot.

The change is largely being taken in stride, with little rancor from opponents and a sense from supporters that same-sex marriage was long overdue. Britain had already allowed gay couples to adopt children, and gay service members are permitted to serve openly in the military.

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Unlike in the United States and other countries that have been roiled by debates over gay rights, marriage equality has overwhelming support here, and was passed by a comfortable majority in Parliament in July.

Leaders of all three main parties — including the ruling Conservatives — backed the bill, and Prime Minister David Cameron championed its passage.

In an article for the Web site PinkNews published late Friday, Cameron hailed the new law. “It says we are a country that will continue to honour its proud traditions of respect, tolerance and equal worth,” Cameron wrote for the Web site, which describes itself as Europe’s largest gay news service. “It also sends a powerful message to young people growing up who are uncertain about their sexuality. It clearly says ‘you are equal’ whether straight or gay.”

The lack of outspoken opposition reflects how quickly attitudes have changed in a country where, just a generation ago, same-sex couples were described by law as “a pretended family relationship,” and schools were banned from doing anything that might promote homosexuality.

“It’s definitely a landmark moment,” said Richard Lane, spokesman for the gay rights advocacy group Stonewall. Same-sex relationships, he said, will now be recognized as “just as loving, united and, frankly, mundane as everyone else’s relationships.”

For Powell and Keith, the legislation came just in time. They could have married when they arrived in their new home in New York — one of 17 U.S. states, plus the District of Columbia, that allow same-sex marriage. But many of their friends and family members in England would have been unable to attend. And the couple wouldn’t have had the satisfaction of getting married in their home country.

“It’s a shame that it took as long as it did. But it ended up being perfect timing,” said Powell, 29, who works as an advocate for student rights and who was to marry in front of 100 friends and relatives at a seaside hotel.

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Despite the change Saturday, the United Kingdom, like the United States, remains a patchwork when it comes to gay-marriage laws. While gay marriage will now be legal in England and Wales, it remains prohibited in the union’s other two component parts: Scotland and Northern Ireland.

The devolved Scottish assembly recently passed legislation that will change that, with same-sex weddings likely by the end of the year. Gay marriage is considered a political non-starter in Northern Ireland, primarily because of vehement opposition from the area’s main Protestant churches and their affiliated political parties. Homosexuality was illegal in Northern Ireland until the early 1980s.

The new law is also opposed by the Church of England, whose bishops wrote a letter last month reminding clergy that “Christian understanding and doctrine of marriage as a lifelong union between one man and one woman remains unchanged.”

But Archbishop of Canterbury Justin Welby appeared to soften the church’s tone this week, suggesting to the Guardian newspaper that clergy would not resist the change. “I think the church has reacted by fully accepting that it's the law, and should react on Saturday by continuing to demonstrate in word and action the love of Christ for every human being,” he said.

The comments echo those of Pope Francis, who has remained adamantly opposed to same-sex marriage but who famously asked in July: “If someone is gay and he searches for the Lord and has good will, who am I to judge?”

Louis Monaco, who grew up Catholic in New Jersey, said he “never thought gay marriage would happen in my lifetime.”

But five years after moving to London, the 46-year-old psychologist would enter his local borough hall Saturday morning and marry his partner of a year and a half, Aarron Erbas. Then they would celebrate at the pub where they met.

“It’s unbelievable,” Monaco said. “Having all my friends there to celebrate with, it’s going to be the best thing ever.”

Karla Adam contributed to this report.