if PEP 431 is implemented (or anything that gives access to zoneinfo)
then strptime could extend the list of timezones it accepts (utc + 
local timezone names) to include names from the tz database:

  import pytz # $ pip install pytz

  {tzname for tz in map(pytz.timezone, pytz.all_timezones) 
   for _, _, tzname in getattr(tz, '_transition_info', [])}

It includes EST.