Description:
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There seems to be a 1 minute (3600 second) error in mktime

Reproduce code:
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$onedayinsecs = 86400;
$timeS = mktime(0, 0, 0, 3, 26, 2006);
$timeS = $timeS + $onedayinsecs;
$dayS = mktime(0, 0, 0, 3, 27, 2006);
echo($timeS." - ".$dayS."<br/>");

Expected result:
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The two values should be the same since we are adding 1 day in 
seconds to mktime value of 3/26/06 and getting the mktime 
value of 3/27/06.

Actual result:
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1143417600 - 1143414000

The difference is 3600. Note if you start at 1/1/06 and go 
through all the days in the year totalling seconds in 
comparison to mktime this error exists between
3/27/06 and 10/29/06. From 30/10/06 the error corrects itself.