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<?php $yr="2012"; $dif=2012-$yr;if($dif < 0) $dif=$dif-1;if($dif > 1) $dif=$dif+1; $week="01"; $day="Monday"; $day=date("D",strtotime($day)); echo date("Y-m-d", strtotime($yr."W".$week."D ".$day)-(86000*$dif));; ?>
Output for 5.2.0 - 5.2.17, 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.28, 7.0.0 - 7.0.20, 7.1.0 - 7.1.10, 7.2.0 - 7.2.33, 7.3.12 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.6
2012-01-02
Output for 5.1.0 - 5.1.6
2012-01-01
Output for 5.0.0 - 5.0.5
2011-12-18
Output for 4.3.0 - 4.3.11, 4.4.0 - 4.4.9
1970-01-01

preferences:
231.77 ms | 402 KiB | 354 Q