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From "John Haxby (JIRA)" <>
Subject [jira] Created: (LUCENE-491) DateTools needs to use UTC for correct collation,
Date Thu, 02 Feb 2006 11:56:03 GMT
DateTools needs to use UTC for correct collation,

         Key: LUCENE-491
     Project: Lucene - Java
        Type: Bug
    Versions: CVS Nightly - Specify date in submission    
 Environment: svn trunk at 02-Feb-2005, noon GMT.  OS independent.
    Reporter: John Haxby

If your local timezone is Europe/London then the times Sun, 30 Oct 2005 00:00:00 +0000 and
exactly one hour later are both converted to 200530010000 by DateTools.dateToString() with
minute resolution.   The Linux date command is useful in seeing why:

    $ date --date "Sun, 30 Oct 2005 00:00:00 +0000"
    Sun Oct 30 01:00:00 BST 2005

    $ date --date "Sun, 30 Oct 2005 01:00:00 +0000"
    Sun Oct 30 01:00:00 GMT 2005

Both times are 1am in the morning, but one is when DST is in force, the other isn't.   Of
course, these are actually different times!

Of course, if dates are stored in the index with implicit timezone information then not only
do we get problems when the clocks go back at the end of summer, but we also have problems
crossing timezones.   If a database is created in California and used in Paris then the times
are going to be badly skewed (there's a nine hour time difference most of the year).

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