Planning promotions in advance makes sense, but unexpected opportunities can sneak up, such as a holiday that fits your genre. You can see a handy calendar with several such dates and/or download a template to create your own here.

Be sure to use the appropriate hashtags for the holiday to fully exploit its usefulness! The reason this method can be effective is that some people will search on the hashtag, which will bring your product to their attention whereas they may have missed it otherwise.