TimeZone details not being honoured in Outlook

[StevenReid]

I have recently received an ICS file containing multiple events that was created using this product.
The events were created for "Eastern Standard Time" and I am in "AUS Eastern Standard Time"
When opening the Time Zone details for the event were not honoured.
The ICS file had TZID information.

When i added the TZID information to each DTSTART and DTEND entry, the correct timezone was added to each event.

[hfloyd]

I am new to this library and using it to create ICS files via a webservice. I have noticed a similar issue with timezones.

(In this example, US Mountain Time, Start time = 11 am, End time 1:30 pm)

When I create the ICS, I add the timezone :

...
    var calendar = new Calendar();

     string tz = TZConvert.WindowsToIana(EventNode.EventTimezone.Id);
     calendar.AddTimeZone(new VTimeZone(tz));
...

And I see it added to the resulting ICS file:

BEGIN:VCALENDAR
PRODID:-//github.com/rianjs/ical.net//NONSGML ical.net 4.0//EN
VERSION:2.0
BEGIN:VTIMEZONE
TZID:America/Denver
X-LIC-LOCATION:America/Denver
END:VTIMEZONE
BEGIN:VEVENT
DESCRIPTION:
DTEND:20220415T133000
DTSTAMP:20220414T163045Z
DTSTART:20220415T110000
...

But when I open the file on my own computer (In USA Eastern Time zone), the timezone displayed is Eastern - BUT, the times haven't been converted properly (it is still showing 11:00 AM - 1:30 PM, when it SHOULD show 1:00 PM - 3:30 PM for the Eastern timezone)

I would expect it to EITHER show the original times in the original timezone (Mountain) OR show the adjusted times in the Eastern timezone...

When I manually change the timezone in Outlook to Mountain time, and save the event - it appears on my calendar in the proper slot for Eastern time:

If I then Save the even as an ICS file and compare it to the generated one, these are the differences:

The main difference seems to be that Outlook is using Windows-style timezones rather than IANA. Additionally, there is all that Daylight saving stuff/offsets, etc. (as already discussed in #58). A bit more searching on the Issues here turned up this other post: #487, which suggests that a change to the generating code would perhaps fix it, so I updated my code to:

...
    var calendar = new Calendar();

    string tz = TZConvert.WindowsToIana(EventNode.EventTimezone.Id);
    calendar.AddTimeZone(VTimeZone.FromDateTimeZone(tz));
...

This did result in a lot more timezone data being added to the generated file:

BEGIN:VCALENDAR
PRODID:-//github.com/rianjs/ical.net//NONSGML ical.net 4.0//EN
VERSION:2.0
BEGIN:VTIMEZONE
TZID:America/Denver
X-LIC-LOCATION:America/Denver
BEGIN:STANDARD
DTSTART:20201101T020000
RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=11
TZNAME:MST
TZOFFSETFROM:-0600
TZOFFSETTO:-0700
END:STANDARD
BEGIN:DAYLIGHT
DTSTART:20210314T020000
RRULE:FREQ=YEARLY;BYDAY=2SU;BYMONTH=3
TZNAME:MDT
TZOFFSETFROM:-0700
TZOFFSETTO:-0600
END:DAYLIGHT
END:VTIMEZONE

But Outlook treated it the same - as if it were in Eastern Time. 😢

I notice that the DTSTART values are different...

Additionally, in the VEVENT data there are some differences:

Outlook adds its time zone name to the DTSTART and DTEND values... (Additionally, I notice that Outlook names the timezone as "Mountain Standard Time", but this event is actually occurring in "Mountain Daylight Time" - but this seems to match up with the way C# TimeZoneInfo objects are identified, so it might not be relevant.)

I decided to try a different tactic - not specifying any timezone info, and changing the provide start and end dates to UTC equivalent times...

But Outlook STILL treated it as Eastern Time - just totally off, since it was using the UTC time values...

I also tried explicitly specifying UTC...

...
    var calendar = new Calendar();

    var tz = "Etc/UTC";
    calendar.AddTimeZone(VTimeZone.FromDateTimeZone(tz));
...

But that made no difference either.

I am kind of stuck now. If anyone has other suggestions, I'd appreciate them.

[hfloyd]

After spending more time googling and testing, I've had a breakthrough today!

According to this post, a "Z" at the end of the DTSTART/DTEND time values indicates UTC time. I did another UTC test to see if the generated file had the "Z" appended. It did not. I looked closer at how I was generating the start/end dates for the event, and realized there were additional overloads for "CalDateTime()" which included tzid as a parameter.

I updated the code I was using to create the start/end dates like this:

new CalDateTime(DateTimeValue, "Etc/UTC");

when I re-ran the generation, the resulting file now had some more information:

BEGIN:VCALENDAR
METHOD:PUBLISH
PRODID:-//github.com/rianjs/ical.net//NONSGML ical.net 4.0//EN
VERSION:2.0
BEGIN:VEVENT
DESCRIPTION:
DTEND;TZID=Etc/UTC:20220415T193000     <------ LOOK HERE
DTSTAMP:20220415T160257Z
DTSTART;TZID=Etc/UTC:20220415T170000   <------ LOOK HERE
LOCATION:
PRIORITY:5
SEQUENCE:0
SUMMARY:Event Test - Mountain Time
UID:3fe8ae15-8f18-4856-8868-791a3b95e6e6
X-ALT-DESC;FMTTYPE=text/html:
X-MICROSOFT-CDO-BUSYSTATUS:BUSY
BEGIN:VALARM
ACTION:DISPLAY
DESCRIPTION:Reminder
TRIGGER:-PT15M
END:VALARM
END:VEVENT
END:VCALENDAR

The date values didn't include the trailing "Z", BUT opening the file in Outlook properly adjusted the time to 1:00 PM - 3:30 PM for the Eastern timezone:

👏🏻🎉

As a final test, I went back to using the specified timezone:

            string tz = TZConvert.WindowsToIana(EventNode.EventTimezone.Id);
            calendar.AddTimeZone(VTimeZone.FromDateTimeZone(tz));
...
            Start= new CalDateTime(DateTimeValue, tz);
            End= new CalDateTime(DateTimeValue, tz);
...

The resulting file included the timezone info on the DTSTART & DTEND values:

BEGIN:VCALENDAR
METHOD:PUBLISH
PRODID:-//github.com/rianjs/ical.net//NONSGML ical.net 4.0//EN
VERSION:2.0
BEGIN:VTIMEZONE
TZID:America/Denver
X-LIC-LOCATION:America/Denver
BEGIN:STANDARD
DTSTART:20201101T020000
RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=11
TZNAME:MST
TZOFFSETFROM:-0600
TZOFFSETTO:-0700
END:STANDARD
BEGIN:DAYLIGHT
DTSTART:20210314T020000
RRULE:FREQ=YEARLY;BYDAY=2SU;BYMONTH=3
TZNAME:MDT
TZOFFSETFROM:-0700
TZOFFSETTO:-0600
END:DAYLIGHT
END:VTIMEZONE
BEGIN:VEVENT
DESCRIPTION:
DTEND;TZID=America/Denver:20220415T133000        <--- HERE
DTSTAMP:20220415T161114Z
DTSTART;TZID=America/Denver:20220415T110000      <--- HERE
LOCATION:
PRIORITY:5
SEQUENCE:0
SUMMARY:Event Test - Mountain Time
UID:92a4d854-6939-4ee0-8c96-3bce4fd5a8d7
X-ALT-DESC;FMTTYPE=text/html:
X-MICROSOFT-CDO-BUSYSTATUS:BUSY
BEGIN:VALARM
ACTION:DISPLAY
DESCRIPTION:Reminder
TRIGGER:-PT15M
END:VALARM
END:VEVENT
END:VCALENDAR

@StevenReid - I think this is what you were looking for?

When I opened the ICS in Outlook, it did NOT show "Mountain Time" as the timezone - but, like for the UTC, It DID adjust the time to 1:00 PM - 3:30 PM for the Eastern timezone.

I do wish MS Outlook would better follow the standard, but this works for my purposes.
I hope this information helps others who are perplexed by timezones in Outlook. 🙂

[afortaleza]

Very helpful @hfloyd, thank you very much.

[hfloyd]

@afortaleza I'm glad to document these things, so someone else can save several hours of trouble 😊