Convert ics files with aware datetimes to new timezone

convert_ics_timezone.py

#!/usr/bin/env python
# vim:filetype=python:expandtab:tabstop=4:shiftwidth=4:
"""
Copied from https://gist.github.com/deybhayden/1980583#file-convert_ics_timezone-py
I observed that dtstart.dt datetime objects were aware (not naive).
There was no need to identify oldtz. Original author's comments left below.

Parag Doke
Asia/Kolkata :-)
-----
Simple script that updates all events in an ical file to a new timezone.
Requires icalendar package (which pulls in pytz as a dependency).

By: @beardedprojamz (Ben Hayden)
"""
import argparse
import sys

import pytz
from icalendar import Calendar
from pytz import timezone

if __name__ == '__main__':
    parser = argparse.ArgumentParser(description='A script to convert an ics calendar & events to the passed timezone.')
    parser.add_argument("--file", "-f", dest='file', help='The ics file to parse and update.', required=True)
    parser.add_argument("--timezone", "-t", dest='timezone', help='The timezone used to update the ics file', required=True)
    args = parser.parse_args()

    cal = Calendar.from_ical(open(args.file, 'rb').read())

    try:
        newtz = timezone(args.timezone)
    except pytz.exceptions.UnknownTimeZoneError:
        sys.exit('Invalid timezone; unable to update ics file.')

    for component in cal.walk():
        if component.name == 'VEVENT':
            dtstart = component.get('DTSTART')
            dtend = component.get('DTEND')
            dtstamp = component.get('DTSTAMP')
            dtstart.dt = dtstart.dt.astimezone(newtz)
            dtend.dt = dtend.dt.astimezone(newtz)
            dtstamp.dt = dtstamp.dt.astimezone(newtz)

    open(args.file, 'wb').write(cal.to_ical())

Thanks! I had to specify an unexpected timezone to get it to do what I wanted but eventually this helped me fix the inaccurately always-UTC-based ics ical export from AirTable's calendar view.