Hello,

 

I'm investigating how to deal with timezones for an application that will get to

processes billions of timestamped events, generated in just about any part of the world.

Timestamps are in local time (without timezone, only post- and other codes) and we need

them in UTC time.  Money is involved, so it is of critical importance that intervals

between events are calculated correctly.

 

There's two steps involved in this:

 

- given some geo data and some lookup tables from a database like geopostcodes.com, determine the timezone id

- convert to UTC using the latest Time Zone Database

 

Development wise it's fairly simple to automate.  We're using joda time and this library allows to

plugin a custom Timezone provider which can then use the latest TZ database.

 

However, I see some issues:

 

1) I noticed that certain timezone ids are deleted in newer versions: tzdata2014a contains

America/Shiprock, newer versions don't.  This may lead to issues whenever recalculations are needed

in the future.  What is the likelyhood that ids are deleted?

 

2) Do rules from the past ever change?  In other words, can we assume that a recalculation of a past

local date to a UTC date will always yield the same result with newer versions of the TZ database? 

If so, is this a common thing and would one then recommend saving the TZ database version with

which the conversion was performed along with the UTC date?

 

Hope one of you can shed some light!

Cheers,

Joris