Description:
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strtotime("- x month") will not work properly when 
around a month change. The following code example was 
run on 31.march. I have seen the previous bug reports 
that indicate that month is really an alias for 30.5 
days. However, this causes problems when you need to 
correctly iterate (dynamically) with the month keyword. 
It should iterate correctly when its specified as month, 
if not my opinion is that implementations should use 
strtotime("- ".$num*"30.5"." days");

Reproduce code:
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for( $c=0;$c<12;$c++ )
 echo date("F",strtotime("-".$c." month"))."<br>";

Expected result:
----------------
March
February
Januar
December
November
October

Actual result:
--------------
March
January
December
December
October
October
...