//parses some string into that format.
datetime1 = datetime.strptime(somestring, \"%Y-%m-%dT%H:%M:%S\")
//gets the seconds from the above date.
timestamp1 = time.mk
I think you can use the utcoffset() method:
utc_time = datetime1 - datetime1.utcoffset()
The docs give an example of this using the astimezone() method here.
Additionally, if you're going to be dealing with timezones, you might want to look into the PyTZ library which has lots of helpful tools for converting datetime's into various timezones (including between EST and UTC)
With PyTZ:
from datetime import datetime
import pytz
utc = pytz.utc
eastern = pytz.timezone('US/Eastern')
# Using datetime1 from the question
datetime1 = datetime.strptime(somestring, "%Y-%m-%dT%H:%M:%S")
# First, tell Python what timezone that string was in (you said Eastern)
eastern_time = eastern.localize(datetime1)
# Then convert it from Eastern to UTC
utc_time = eastern_time.astimezone(utc)