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<?php $t = '1/99999'; list($m,$d)=explode("/",$t);$m%=12;$d%=365;$i=0;while($d>100)$d-=[31,28,31,30,31,30,31,31,30,31,30,31][$i++];$m+=$i;echoDateTime::createFromFormat("m/d","$m/$d")->format("n/j");

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63.89 ms | 402 KiB | 5 Q