The calendar should send to server:
- for an all day event (all_day field on view): the date in UTC (ie. if
we are on 22 august 2018 on UTC+2, not send 21 august 2018 22:00)
- for a datetime event not all day: the UTC datetime corresponding to
UTC (for 03:25 with UTC+5 timezone, we send 22:25 the day before)
- for a date event: the date in UTC (ie. same as all day)
The current code was alright for datetime, but there was a missing case
if the start_date was a Date field (eg. project task calendar view uses
a date_deadline Date field) and not a Datetime field.
This changeset apply the same behavior as an all_day event to a calendar
with a start date that is a Date field.
Note: the issue happen since 11.0's 03d74f4 (26th march 2019) that
solved a similar case but for datetime (a datetime event at 8:00 with
timezone UTC+9 would be moved the previous day when drag and dropped on
the month view).
opw-1969876
opw-1971106
opw-1971019
closes#32796
Signed-off-by: Adrien Dieudonné (adr) <adr@odoo.com>