You can find out what times your posts will go out by visiting the SCHEDULE page via the SCHEDULE link near the COMPOSE button.
When you connect your social account to Stacker a default posting schedule is created for your account. You can view this schedule by selecting the account on the left.
You can also customize this schedule. Simply select the timezone, days and times you want the posts to go out and Stacker will automagically post your content
Note: If you are on the FREE plan you can only select Post at the Same time Every day. The Post at Different times Each day is only available for the PAID plans