Beanz: There is a keyword "holiday". See https://www.imdb.com/search/keyword/?keywords=holiday for a list of titles with that keyword.

However, to be more specific and get a longer list, you may be looking for the keyword "christmas" instead: https://www.imdb.com/search/keyword/?keywords=christmas

It seems unlikely to me that IMDb will ever establish a Holiday genre, though. The IMDb staff announced plans to create five additional genres -- Soap Opera, Erotica, Awards Show, Experimental, and Lifestyle -- but apparently they have found it very difficult to actually implement those genres. We have been waiting for those genres to be implemented since the year 2010. See the thread at https://community-imdb.sprinklr.com/conversations/data-issues-policy-discussions/implementation-of-new-genres/5f4a7a638815453dbaa6da98 for more information. 

Other relevant keywords (assuming you were looking for Christmas movies):

https://www.imdb.com/find/?s=kw&q=christmas