note 17457 deleted from function.mktime by jimw

An amendment to my post above: I ran the function through a for loop, increasing the year each time. Half the years the output is accurate. %25 of the years the output is a day ahead, and 25% of the time it is a day late. Here is the script I ran: for($i=1990; $i<2006; ++$i) { $lastday = mktime (0,0,0,12,0,$i); echo strftime ("Last day in Nov, $i is: %m %d", $lastday); } And here is my output: Last day in Nov, 1990 is: 11 30 Last day in Nov, 1991 is: 11 30 Last day in Nov, 1992 is: 11 29 Last day in Nov, 1993 is: 12 01 Last day in Nov, 1994 is: 11 30 Last day in Nov, 1995 is: 11 30 Last day in Nov, 1996 is: 11 29 Last day in Nov, 1997 is: 12 01 Last day in Nov, 1998 is: 11 30 Last day in Nov, 1999 is: 11 30 Last day in Nov, 2000 is: 11 29 Last day in Nov, 2001 is: 12 01 Last day in Nov, 2002 is: 11 30 Last day in Nov, 2003 is: 11 30 Last day in Nov, 2004 is: 11 29 Last day in Nov, 2005 is: 12 01 Can anybody tell me what could possibly be causing this?