My guess is that he set his timezone in his user settings. If so, it’ll display the time as “7pm CDT”. I noticed the timezone of the person who saw 7pm was not mentioned, but everyone else explicitly saw EDT.
If you too want to change the site to show everything in your local timezone, you can learn more about it in this thread:
Obviously simply being in a location where Central Time is observed is not enough as the site does not track your location in any way.