tl;dr I couldn't find a social media calendar for video games specifically so I made one. Enjoy.
I should probably preface this with a definition- what is a social media calendar? According to CoSchedule:
Social media editorial calendars are spreadsheets or apps used to schedule social posts in advance. They're also used to plan when and which content will be shared, manage campaigns, and track deadlines.
So, I made my own.
These are a few suggestions for each day to post about you're games- some days have prominent hashtags (mainly on twitter) but every day has a suggestion on what to post in general.Wednesdays and Saturdays are typically the biggest in terms of relevant content you can post, given that they both have 2 large tags that are very relevant to game dev. This list is mainly for Twitter, but can be referenced for other social media sites.