Calculate date from day of year in php

Here  is a simple first of several notes on useful date functions.  This function accepts  a year  (YYYY) and a Day in the year (1 to 366), and returns a DateTime Object.

 /* Year if format YYYY, Day in year 1 to 366 */
function dayofyear2date( $year, $DayInYear ) {
$d = new DateTime($year.'-01-01');
date_modify($d, '+'.($DayInYear-1).' days');
return ($d);
}

I’m tired of seeing Unix time stamp code examples that break with older dates. Since my ical calendar scripts can potentially hold recurring dates that are anniversaries and birthdays, my scripts need to cope with dates earlier than 1970, and with timezones and daylight saving, so I use the DateTime class exclusively now.

Test Script To Check Function

<?php

function dayofyear2date( $year, $DayInYear ) {
 $d = new DateTime($year.'-01-01');
 date_modify($d, '+'.($DayInYear-1).' days');
return ($d);
}

$d[] = new DateTime('1950-12-31');
$d[] = new DateTime('1970-01-01');
$d[] = new DateTime('2010-01-01');
$d[] = new DateTime('2010-12-27');
$d[] = new DateTime('2010-12-31');

foreach ($d as $i => $d2)    {
 $dayofyear = $d2->format('z')+1;
 $date = dayofyear2date (
 $d2->format('Y'),
 $dayofyear ); /* note z returns days from 0 */
 echo '<br /><b>'.$d2->format('Y m d')
  .'</b>&nbsp;&nbsp;'.$dayofyear.'&nbsp;&nbsp;<br />'
  .$date->format('Y m d');
}
?>

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