ISO 8601 UTC timestamp recipe

time_conversions.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
Here we use timezone-aware datetime objects, as opposed to timezone-naive ones.

Source: Python manuals, stackoverflow posts, trial and error.
"""

from datetime import datetime
import time
import pytz
import dateutil.parser

# i.e. datetime.datetime(1970, 1, 1, 0, 0, tzinfo=<UTC>)
epoch = datetime.fromtimestamp(0, pytz.utc)

# e.g. 1453173767.139255
seconds_since_UNIX_epoch = time.time()

# e.g. datetime.datetime(2016, 1, 19, 3, 22, 47, 139255, tzinfo=tzutc())
timestamp = datetime.fromtimestamp(seconds_since_UNIX_epoch, pytz.utc)

# e.g. '2016-01-19T03:22:47.139255+00:00'
iso_timestamp_string = timestamp.isoformat()

# e.g. datetime.datetime(2016, 1, 19, 3, 22, 47, 139255, tzinfo=tzutc())
back_again = dateutil.parser.parse(iso_timestamp_string)

# A time_delta object: datetime.timedelta(16819, 12167, 139255)
td = (back_again - epoch)
# e.g. 1453173767.139254
td_seconds = td.total_seconds()

# CHECK:
# Verify that we got back to where we started
# Use approximate check because of floating point epsilon as per
# https://www.python.org/dev/peps/pep-0485/
import sys
if sys.version_info[0] >= 3 and sys.version_info[1] >= 5:
    from math import isclose
else:
    def isclose(a, b, rel_tol=1e-09, abs_tol=0.0):
        return abs(a-b) <= max(rel_tol * max(abs(a), abs(b)), abs_tol)

assert(isclose(seconds_since_UNIX_epoch, td_seconds))