At the stroke of midnight, thousands of same-sex couples who married in overseas jurisdictions had their vows recognised under Australian law.

For many who decided not to wait for same-sex marriage to become a reality back home, they instead exchanged vows under foreign laws in countries like New Zealand.

Others, like Amy and Amanda Keeling from Sydney's northern suburbs, found a means to tie the knot closer to home. Two years ago, they decided to marry at the British consulate in Sydney.

"We didn't want to wait for marriage equality in Australia because we were starting a family and we thought it was important for us to begin that journey of marriage," explained Amanda, who is a dual Australian-British citizen.

Amy and Amanda are among 450 couples in Australia who have taken this diplomatic route to tie the knot.

"I was always taught that you would grow up, go to school, maybe meet someone special, get married, have kids, and so on," Amanda said.

"I wanted that whole dream."

Amanda and Amy did not want to wait to get married because they were starting a family. ( Supplied )

There were tears in the Keeling household on Thursday, as they watched the extraordinary scenes unfold in Parliament on TV.

"Our two-year-old came up and said, 'What's wrong Mummy?"' Amanda said.

"I was like, 'Nothing's wrong. For once, nothing is wrong'."

"He knows that we are excited about being married," Amy said.

"Whatever that means to a two-and-a-half-year-old!"

First weddings able to happen from January 9

Under the Marriage Amendment Bill, Australian law will not only recognise marriages undertaken overseas, but also marriages sworn in the presence of a diplomatic officer of a foreign country.

For the Keelings, last night marked the end of a very long journey.

"It means I can say with faith to my sons that we are just as valued as a family unit as anybody else, and that he can see that reflected in the laws and practices of our society," Amy said.

Amy and Amanda said there would be no partying for them after the decision, because they could not find a babysitter. ( ABC News: Greg Heaps )

The momentous occasion was not marked with late night partying though — Mrs and Mrs Keeling could not get a babysitter on such short notice.

"[We'll be] just hanging out at home, making dinner, doing bath-time, putting them to bed, reading stories and probably having a little chat to them in two-and-a-half-year terms about the significance of what happened today."

Attorney-General George Brandis has said couples would have to give a month's notice of their intention to marry, so the first same-sex weddings will be able to happen from January 9, 2018.

Accordingly, ceremonies for same-sex couples will continue in British consulates until at least January 9.