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On 01/06/14 00:36, Joris Van den Bogaert wrote:
<blockquote cite="mid:8B420C0278CD45B6A88ADD70FB376A0E@WhizzitPC"
type="cite">
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<div>Hello,</div>
<div> </div>
<div>I'm investigating how to deal with timezones for an
application that will get to</div>
<div>processes billions of timestamped events, generated in
just about any part of the world.</div>
<div>Timestamps are in local time (without timezone, only
post- and other codes) and we need </div>
<div>them in UTC time. Money is involved, so it is of
critical importance that intervals </div>
<div>between events are calculated correctly.</div>
<div> </div>
<div>There's two steps involved in this:</div>
<div> </div>
<div>- given some geo data and some lookup tables from a
database like geopostcodes.com, determine the timezone id</div>
<div>- convert to UTC using the latest Time Zone Database</div>
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</blockquote>
Matching geo data to a timezone is a bit fuzzy. On the <br>
other hand, you state that correct calculation is critical.<br>
<br>
<br>
<br>
<blockquote cite="mid:8B420C0278CD45B6A88ADD70FB376A0E@WhizzitPC"
type="cite">
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<div>2) Do rules from the past ever change? In other words,
can we assume that a recalculation of a past </div>
<div>local date to a UTC date will always yield the same
result with newer versions of the TZ database? </div>
<div>If so, is this a common thing and would one then
recommend saving the TZ database version with </div>
<div>which the conversion was performed along with the UTC
date?</div>
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</blockquote>
Yes. If new data is discovered and it turns out the previous rule <br>
was wrong, it is updated. The new one will (hopefully) be more <br>
accurate, but there will be a difference from converting with the <br>
previous version.<br>
Also note that the applicable timezone could change.<br>
<br>
You may know more than us how likely it is that the information <br>
about the period you are treating wasn't accurate.
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Now I'm thinking that perhaps you aren't working on historic <br>
records but with future ones, in which case it's very likely that<br>
tz will be right (but in that case why not store them in UTC
directly?)<br>
… excluding the cases where a Government decides to change time <br>
and tz/your team is not able to provide/install the new rules before
<br>
the change. :/<br>
<br>
<br>
<br>
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