Put all-day events into the right timezone

[nmlorg]

Someone just added an event to their calendar for someone's birthday (on Sat, Jul 20), and it's being treated as a 24-hour event from 5 p.m. tomorrow (Fri, Jul 19) until 5 p.m. the next day because the API returns:

items:
- created: '2024-07-18T15:44:44.000Z'
  description: ...
  end:
    date: '2024-07-21'
  eventType: default
  kind: calendar#event
  reminders:
    useDefault: false
  sequence: 0
  start:
    date: '2024-07-20'
  status: confirmed
  summary: ...
  transparency: transparent
  updated: '2024-07-18T15:44:56.837Z'
kind: calendar#events
timeZone: America/Los_Angeles
updated: '2024-07-18T15:44:56.837Z'

and m.c.google.Calendar.datetime_proto_to_local just passes '2024-07-20' through:

metabot/metabot/util/iso8601.py

Lines 7 to 22 in d0110b6

	def totimestamp(isoformat):
	"""Convert a string like YYYY-MM-DDTHH:MM:SS+HH:MM to the number of seconds since 1970-01-01."""
	year, month, day, _, hour, minute, second, fraction, _, utchour, utcminute = re.match(
	r'(\d{4})-?(\d{1,2})-?(\d{1,2})'
	r'(T(\d{1,2}):?(\d{1,2}):?(\d{1,2})'
	r'([.]\d+)?'
	r'(([-+]\d{1,2}):?(\d{1,2})|Z)?'
	r')?$', isoformat).groups()
	dtime = datetime.datetime(int(year), int(month), int(day), int(hour or 0), int(minute or 0),
	int(second or 0), int(1000000 * float(fraction or 0)))
	if utchour and utcminute:
	tzinfo = _TimeZone(int(utchour) + float(utcminute) / 60)
	else:
	tzinfo = _UTC
	return (dtime.replace(tzinfo=tzinfo) - _EPOCH).total_seconds()

which correctly (if naively) gives midnight UTC on 2024-07-20 (which is 5 p.m. the day before in America/Los_Angeles).

Somewhat weirdly, non-all-day events include time zone information in both the date spec and a separate timeZone field:

  end:
    dateTime: '2024-07-20T19:30:00-07:00'
    timeZone: America/Los_Angeles
  start:
    dateTime: '2024-07-20T14:30:00-07:00'
    timeZone: America/Los_Angeles

and m.c.google just relies on m.u.iso8601 extracting the '-07:00' to adjust things correctly. However, while all-day events don't include any time zone information at all, service.events().list() still returns the calendar's default time zone, so theoretically that could be extracted and bundled in (though that would mean m.u.iso8601 would either need to switch entirely over to using pytz, or use two entirely different approaches for doing time zone calculations).

---

It is possible for a calendar to have one default time zone and a Telegram group to configure the bot to present events in a different time zone, in which case even with the above the events will still not run midnight to midnight.

Alternatively, the all-day nature of the event could be preserved all the way out to m.u.eventutil.format_event, but I'm leaning toward ignoring this until I see it actually happening. (All-day events in general are pretty rare in practice.)

[nmlorg]

Updated:
• XXX’s Birthday was moved back to Sat 20ᵗʰ, 12ᵃᵐ (from Fri 19ᵗʰ, 5ᵖᵐ; same duration).