Vincent Orange won the last citywide special election, on April 26, 2011. (The Washington Post)

The D.C. Board of Elections met Thursday morning to certify the results of the general election and to set the date of the coming special election to fill the at-large D.C. Council seat that previously belonged to Phil Mendelson.

In days of yore, there wasn’t much involved in picking a special election date except pulling out a calendar and doing some math. The city charter set the date as the first Tuesday at least 114 days after a vacancy is declared. But that changed after the 2011 election, during which a D.C. rabbi sued the city after it set Election Day for the final day of Passover, a Jewish high holy day.

In settling the case, the city agreed to seek more flexibility in setting special election days to avoid religious holidays. Congress passed a bill doing so earlier this year, and the election board for the first time had the discretion to pick a date between 70 and 174 days after the vacancy is declared.

The board picked April 23, which is about a month later than Election Day would have been had the old law been in place.

Clifford Tatum, the board’s executive director, said several factors were taken into account, including religious and government holidays, the time necessary to prepare for the election, and the weather.

“We determined that the 23rd would be the best day to avoid those types of conflicts,” he said. “Doing anything earlier than April puts us in some precarious weather situations. … We couldn’t do it really any earlier.”

The later date means the interim appointee, to be selected by Democratic Party officials on Dec. 10, will get an extra month in office than he or she might otherwise have enjoyed.

Candidates interested in running in the special election can pick up nominating petitions starting Dec. 6. To appear on the ballot, they will have to collect signatures from 3,000 District voters by Jan. 23.