Normalizing Windows TZIDs to IANA on write?

[abe-101]

Normalizing Windows TZIDs to IANA on write?

I'm pulling in several .ics feeds on a Linux server (some from Outlook/Exchange) and merging them. The Outlook ones come through with Windows TZIDs like:

DTSTART;TZID=Eastern Standard Time:20260422T110000

The reason I want to normalize: on my web project that renders the merged calendar, the client doesn't seem to understand the Outlook/Windows TZID and just falls back to the viewer's local time — which shows the wrong time.

On read, icalendar seems to resolve these correctly to America/New_York (I think via WINDOWS_TO_OLSON and TZP.timezone()) — but when I call to_ical(), the Windows name still comes out in the TZID param and VTIMEZONE.

A few questions:

1. Is there already a supported way to get IANA names on write that I'm missing?
2. If not, would it make sense to expose something for this - maybe a flag on to_ical() or a helper — and is that something the project would want?
3. Any gotchas I should know about?

[niccokunzmann]

Hi, if you like that, you are welcome to contribute something. Personally, I would prefer if you describe first how you would like to use this feature in the nicest and most comfortable way without thinking about implementation. That yields the most intuitive and friendly interface. Use-case, examples and documentation first.

If you use Calendar.to_ical() make sure it does not introduce side-effects.
You can also add a method to the calendar to convert OLSON TZIDs to Iana.
Of course, that can also be part of another package.

Is there already a supported way to get IANA names on write that I'm missing?

Not in icalendar as far as I know. It is very a very specific use-case and so would be hard to find anywhere else but also very useful to have in here.

If not, would it make sense to expose something for this - maybe a flag on to_ical() or a helper — and is that something the project would want?

Yes, that is wanted.

Any gotchas I should know about?

• We use iana timezones anyway. As such, you could convert a calendar in-place - to align the timezone names to what is in use anyway.
• Make sure the VTIMEZONE is also changed, not just the TZID.

I think, this is it. It is probably useful to convert windows to linux for downstream. It could be nice to offer this as a CMD tool somewhere (small, additional package :)