Sen. Richard Madaleno, center, celebrates onstage at an election night party in Baltimore last month after voters passed a mesaure approving same-sex marriage in Maryland. (AP Photo/Patrick Semansky)

Gay couples planning to wed Jan. 1 will be able to get post-dated marriage licenses as early as Thursday in some Maryland counties, officials said Wednesday.

“We hope to be all set for tomorrow,” said Loretta E. Knight, clerk of the circuit court in Montgomery County. “If someone wants to have a New Year’s Eve party and get married here afterwards, they can.”

Last month, Maryland voters upheld the state’s new same-sex marriage law, which takes effect on Jan. 1. That’s a court holiday, but clerks can issue licenses early to accommodate couples who want to get married on New Year’s Day, according to an opinion issued last week by the state Attorney General’s Office.

The opinion said clerks could start issuing the post-dated licenses as soon as the governor formally declares that Question 6 was passed by voters. Gov. Martin O’Malley (D) is planning to sign a proclamation to that effect Thursday morning, his office said Wednesday.

Knight, who also is president of the Maryland Association on Circuit Court Clerks, said she understands that clerks in about two-thirds of the state’s counties plan to issue licenses before Jan. 1.

Prince George’s County is among those, but it is unlikely to start Thursday because of computer programming changes required to carry out the policy, Knight said. A call to the clerk’s office in Prince George’s was not immediately returned Wednesday afternoon.

In counties that do not issue licenses until Jan. 2, same-sex marriages will not take effect before Jan. 4. That’s because Maryland has a two-day waiting period for licenses to take effect after they are issued.

Question 6, the ballot measure upholding the gay marriage law, passed 52 percent to 48 percent last month.