Building off the answers provided, one needs to be aware of differences in relative date formatting between php 5.2 and php 5.3.
TEST:
$date1 = strtotime("first wednesday of 2010-12");
$date2 = strtotime("first wednesday 2010-12");
$date3 = strtotime("wednesday 2010-12");
5.2 Results:
1969-12-31
2010-12-08
2010-12-01
5.3 Results:
2010-12-01
2010-12-08
2010-12-01
Therefore only the third method returns correct results across PHP 5 versions.