Example of how to convert: [localised timestamp] <-> [timestamp in UTC encoded in ISO string and UTC offset in seconds].

timestamps-encoding-localised_to_utc.py

import datetime
import pytz
import dateutil.parser

from typing import Tuple


def encode(ts: datetime.datetime) -> Tuple[str, float]:
    """Return string encoding timestamp in UTC in ISO format and timezone offset in seconds."""
    if ts.tzinfo is None:
        raise Exception(f"Provide localised timestamp: tzinfo={ts.tzinfo}")
    utc_ts = pytz.utc.normalize(ts)
    utc_offset = ts.utcoffset()
    return utc_ts.isoformat(), utc_offset.total_seconds()


def decode(utc_ts: str, utc_offset: float) -> datetime.datetime:
    """Construct timestamp from the string encoding timestamp in UTC in ISO format and timezone offset in seconds."""
    ts = dateutil.parser.isoparse(utc_ts)
    if ts.tzinfo != dateutil.tz.tzutc():
        raise Exception(f"Provide timestamp in UTC. You provided: {ts.tzinfo}")
    return ts.astimezone(dateutil.tz.tzoffset(name=None, offset=utc_offset))


if __name__ == "__main__":
    t = datetime.datetime.now()
    assert t.tzinfo is None

    timezone = pytz.timezone("Europe/Zurich")
    t_localised = timezone.localize(t)

    utc_ts, utc_offset = encode(t_localised)
    assert decode(utc_ts=utc_ts, utc_offset=utc_offset) == t_localised