No. If you create a social message in the edit page of a post, this message will be associated to that post and its publication date will change in the same way the publication date of the post does.
However, if you create the social message directly from the editorial calendar, this message won’t be associated to any post–it will be an independent message and you’ll be able to freely reschedule it.
To achieve this, just use the proper action on one of the sides of the calendar:
Another option is to use the same action but from a specific day on the calendar. Simply put your mouse on the day you want and the previous actions will appear, as you can see here:
Once you select the action to add a new social message, the following dialog will appear. There, complete the information of the new message:
After completing the information, confirm and you’ll create a social message that won’t be associated with any post.