[tz] Non-valid timezones, is there a rule to remove them?

[Paul_Koning at Dell.com]

On Jan 23, 2014, at 9:08 AM, Patrice Scattolin <patrice.scattolin at oracle.com> wrote:

> For example, if your are in Argentina/San_Juan and your calendar has a meeting in the past (for legal reasons you are keeping track of your meetings) where the zones were different, the rule is still in force. Were the Argentina/San_Juan removed that meeting time would then move by 1h when applying Argentina/Buenos Aires in place. 

Exactly.  I think the confusion is what the timezone data is used for.

If you think it is ONLY used to display the correct current local time given a UTC time reference, then the notion of an “invalid” time zone makes sense.

But in fact that’s only one small application.  The bigger picture is that you have a lot of applications that store timestamps for events that may go back decades.  Calendar is an example.  File system time stamps, or source control timestamps, are another.  It is essential that such timestamps are interpreted correctly.  And to do that, you must have a database that tells you the UTC to local time mapping for all time stamp values of interest.  

For a lot of us, that means timestamps back to the Unix epoch (1970). For some, it means timestamps back a lot farther than that.

	paul