How to store TimeZoneInfo objects in a database?

Question

Somewhat misleading title, I know. Never actually wanted to store TimeZoneInfo object themselves: rather, I want to store some culture-neutral identifier, which can

Answer 1

Yes, Id is a non-localized identifier, so that's an appropriate thing to store.

You should be aware of one possible problem though: identifiers can change over time. I don't know whether it's an issue in Windows time zone identifiers, but it certainly occurs in the Olson (zoneinfo) database. For example, I was recently looking at an issue caused by "Pacific/Ponape" changing to "Pacific/Pohnpei".

I suspect that as Microsoft has tighter control over the IDs, they're more likely to remain the same - but even so, countries can change their names, split into different countries (potentially creating new time zones) etc.

I'm not suggesting any fixes for this problem - just highlighting it as a potential issue. Storing the ID is probably the best approach available, but be aware of the potential risks...

Answer 2

I don't see an issue with storing the IDs, as they appear to be a constant value across the windows platform - that is, a specific ID will always map to the same TimeZoneInfo object, regardless of which version of windows you use.

I am not sure what mono does, but I would not be surprised if this would be the same. You can always check the class source code.

Answer 3

check these two methods

public static System.TimeZoneInfo FromSerializedString(string source)
public string ToSerializedString()

these should preserve as much info as possible :)

Answer 4

I simply used TimeZoneInfo.Id.GetHashCode(). According to tests, this generates unique integer ID's that can be stored in a DB. You can also build a Dictionary with keys being these hash codes and values being the original ID strings to make reverse lookup easier.