Dark days and cold nights bring Christmas ratings gifts to syndication, particularly in the access hour, with offnet sitcoms and evening gameshows benefiting from bigger TV audiences in the evening.

Sitcoms, in particular, tend to grow in the winter, while most daytime shows remain stable. Warner Bros.’ offnet rookie “The Big Bang Theory” premiered in September at an already healthy 4.5 live-plus-same-day national household rating, according to Nielsen. By the week ending Dec. 4, “Big Bang” already had added 37% more households to reach a 6.2, including its robust primetime run on TBS.

That growth is expected to continue into February sweeps, when sitcoms tend to hit their stride. Warner Bros.’ “Two and a Half Men” premiered in 2007 at a 3.3. By February 2008, it had grown 66% to a 5.5.

Today, “Two and a Half Men” remains syndication’s leading offnet sitcom at a 6.5, on par with its fifth-season syndication premiere in September. In second and third place, Twentieth’s two strong contenders, “Family Guy” and “How I Met Your Mother,” also have gained since September, with “Family Guy” adding 5% for a 4.2 and “Mother” improving 11% (3.6). “Mother” also has added a run on FX, which is boosting its numbers.

The rest of the genre also is up or flat, with only two veteran shows — Twentieth’s “King of the Hill” and Carsey Werner’s “That ’70s Show” — declining, off 5% and 15%, respectively.

Sitcoms aren’t the only shows that benefit from darker days. All of the gameshows are up, with CBS Television Distribution’s “Wheel of Fortune” leading all of syndication at a 7.6, up 16% and a full ratings point from its September premiere of 6.6. CTD’s “Jeopardy!” also has added viewers since September, growing 14% to a 6.2.

Debmar-Mercury’s “Family Feud,” which airs predominantly in daytime and early fringe, is continuing its ratings rise, adding 11% for a 3.1. Disney-ABC’s long-running daytime quizshow “Who Wants to be a Millionaire” is flat from its season start at a 2.5.