gnome-calendar doesn't import ics files correctly

gnome-calendar doesn't import ics files correctly.

1. I downloaded public ics files like https://www.calendarlabs.com/ical-calendar/ics/76/US_Holidays.ics Their entries were shown in gnome-calendar, but not in gnome's date & time. In gnome-calendar they had an end date before the start date.

The ics files from calendarlabs don't implement the standard from https://tools.ietf.org/html/rfc5545#section-3.6.1 for VEVENTs correctly. While the DATE from DTSTART is inclusive, the DATE from DTEND isn't. For a one day event DTEND's DATE has therefore to be one day after DTSTART's date.

Some programs correct this by simply increasing DTEND by one day in these cases and gnome-calendar should do that too. As no event can end before it starts, gnome-calendar's behavior of setting the end date before the start date doesn't make sense.

2. If a VEVENT has a DTSTART property with a DATE but no DURATION and no DTEND property, according to https://tools.ietf.org/html/rfc5545#section-3.6.1 "the event's duration is taken to be one day." I therefore deleted the DTEND property in for instance US_Holidays.ics and expected that now gnome-calendar would import the ics file's VEVENTS correctly. But even in this case of standard conforming ics files gnome-calendar imported them with an end date before the start date. This time without the need to correct an error, but simply the need to implement a standard correctly.

In both cases gnome-calendar shouldn't produce events with a end date before the start date.

I used apport but again: I have ubuntu 20.04.2 LTS and an up to date gnome-calendar 3.36.2-0ubuntu1.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: gnome-calendar 3.36.2-0ubuntu1
ProcVersionSignature: Ubuntu 5.4.0-70.78-generic 5.4.94
Uname: Linux 5.4.0-70-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.16
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: ubuntu:GNOME
Date: Mon Mar 29 02:46:12 2021
InstallationDate: Installed on 2018-08-10 (961 days ago)
InstallationMedia: Ubuntu 18.04.1 LTS "Bionic Beaver" - Release amd64 (20180725)
ProcEnviron:
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: gnome-calendar
UpgradeStatus: No upgrade log present (probably fresh install)