If you create a template that joins the timestamp and the 3 digit code for your timezone (not sure if or what they are), or if you add -5 or GMT-5, then it will lock that timestamp to a specific timezone and adjust accordingly, based on the user’s timezone.
I also have an app that converts local time to GMT time if you wanted to calculate and store all timestamps in a standard universal time.
Also, there is a new plugin that will do this conversion as well. Haven’t played with it yet.