The presence of the SOLIDUS character as a prefix, indicates that

this "TZID" represents a unique ID in a globally defined time zone

registry (when such registry is defined).

Note: This document does not define a naming convention for

time zone identifiers. Implementers may want to use the naming

conventions defined in existing time zone specifications such

as the public-domain TZ database [TZDB]. The specification of

globally unique time zone identifiers is not addressed by this

document and is left for future study.

Actually, all Calendar apps/parsers recognize the TZID timezones as defined originally by Microsoft. And you can generate the file yourself, it doesn't have to come from Outlook. – Noah David Aug 5 '15 at 19:14

    

This is far from the thruth. I would say most people use and support the olson timezones, with the exception of microsoft products. You'll get a wider coverage if you use just olson timezone names. – Evert Aug 5 '15 at 20:53

    

I don't know about that... to create a properly recognized Outlook Calendar ICS file, that works with Timezones, you MUST use the TZID as I documented here on a blog years ago when I worked for Nokia Siemens Networks: hello-dot-wordpress.blogspot.com/2009/10/… Google Calendar, Apple Calendar, and every other calendar product I've used over the years respects the TZID entry in the ICS files -- so it's probably best to use the method that's supported across ALL platforms, not "most" of them as you described above. – Noah David Aug 6 '15 at 17:49