We have a project which has multiple shift types, to solve this while staying as native as possible within Odoo, we thought about creating multiple resource.calendar entries, and add a new calendar_id field linked to a planning.role. Doing so allows us to create the planning.slot.template's for each role (in this case, a shift), and compute the durations with the linked calendar instead of the companys calendar.

With the given example, where a guard will start at 21:00 and end on 08:00 of the next day, the expected end_time and duration_days are 8 and 1 respectively.

The issue is located at the plan_hours function from enterprise/resource/models/resource.py, more precisely:

def plan_hours(self, hours, day_dt, compute_leaves=False, domain=None, resource=None):
	# hours: 11
	# day_dt: datetime.datetime(2024, 3, 18, 21, 0, tzinfo=<DstTzInfo 'Europe/Madrid' CET+1:00:00 STD>)
	# compute_leaves: True
	# ...
	if hours >= 0:
		delta = timedelta(days=14)
		for n in range(100):
			dt = day_dt + delta * n
			for start, stop, meta in get_intervals(dt, dt + delta)[resource_id]:
				interval_hours = (stop - start).total_seconds() / 3600
				if hours <= interval_hours:
					return revert(start + timedelta(hours=hours))
				hours -= interval_hours
		return False

The variable stop is using 999999 milliseconds, which produces the issue when hours -= interval_hours is evaluated

# hours: 11
# interval_hours: 2.999999999722222

# hours (next loop): 8.000000000277778
# interval_hours (next loop): 8

Since hours is bigger than interval_hours, instead of returning dt(2024, 3, 19, 8), it continues evaluating the loop until dt(2024, 3, 19, 21, 0, 0, 1) is returned.