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List:       sqlite-users
Subject:    Re: [sqlite] Difference between localtime and utc is 8 hours, but should be 4
From:       Chris Waters <cwaters () watershed ! com ! au>
Date:       2017-04-23 9:35:05
Message-ID: 2157FF95-E82B-4179-8DA4-CFAFF62543C7 () watershed ! com ! au
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As Stephen observed when replying to your query, time math is fraught with problems.

So I think it will be nothing to do with SQLite per se. I'm guessing it will be in \
the time offset specification you have entered somewhere, for your environment. You \
are in what is termed time zone utc  -4. Time zones are expressed as what you have to \
do to UTC to get your local time. So for you, -4.  A common error is to express it as \
what you have to do to your local time to get UTC. That expression would be +4 for \
you! Wrong.

I suspect this is where your 8 hour difference is coming from. 

In a layered environment where you have O/S, plus "international" application layers \
such as mail environments and ERPs you have multiple competing transforms, which in a \
round trip (my location back to my location) will appear as everything is set \
correctly, but when you move out of your zone can appear bizarre.

Hope this is useful
Chris
> 
> I'm in the Eastern US time zone, in daylight savings time.  I am four hours earlier \
> than UTC time.  I have a column that stores UTC times as Julian times \
> (floating-point numbers).  The latest data point in the table was stored at about \
> 8:41 this morning (4/21).   
> I am getting strange results from this query:
> select max(value_timestamp), 
> datetime(max(julianday(value_timestamp)), 'localtime'),
> datetime(max(julianday(value_timestamp)), 'utc') from trend_data
> 
> The results are: 
> 2457864.86179398
> 2017-04-21 04:40:59
> 2017-04-21 12:40:59
> 
> How is it that switching from local time to UTC gives an eight-hour difference?
> 
> Thank you very much.
> 
> RobR
> 
> ------------------------------
> 
> 
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