PHP：转换为日期格式的问题

I found the following function on the PHP Manual page that calculates the Orthodox Easter date (source: http://www.php.net/manual/en/function.easter-date.php).

function easterOrthodox_date($year) { 
    $a = $year % 4; 
    $b = $year % 7; 
    $c = $year % 19; 
    $d = (19 * $c + 15) % 30; 
    $e = (2 * $a + 4 * $b - $d + 34) % 7; 
    $month = floor(($d + $e + 114) / 31); 
    $day = (($d + $e + 114) % 31) + 1; 

    $de = mktime(0, 0, 0, $month, $day + 13, $year); 

    return $de; 
}

I am using the following line to get this date for a certain year (selYear):

$EasterOrth = date('Y-m-d', easterOrthodox_date($selYear));

When I echo the result on my page this looks correct and shows 2014-04-20 (which is correct as for this year it is the same date as for the catholic Easter).

However, when I use this for other calculations it returns wrong results, e.g. the Dec 31. Is it possible that in this case I need to format this differently in order to get a date with the format yyyy-mm-dd ?

Update: The above variable is being passed to a stored procedure in SQL where I run the following Select (part of a longer query):

SELECT      DATEADD(d, daysFromEaster, @EasterOrth) AS dayX,
            category1,
            category2,
            '' AS validity
FROM        DayCheck_Easter
WHERE       mode = 'EasterOrth'

This should only fetch items from a table where the mode is set to EasterOrth and it seems the issue is with the first line here where I am adding a number of days (int). It works fine in several other Selects but here it calculates the wrong dates which is why I thought my formatting is wrong so that it isnt recognised as date.

Thanks, Mike.

I found the issue - it was neither the PHP nor the SQL but a typo in the Ajax that passes the variable which is why SQL couldn't read it properly.

Thanks again for all the help - it pointed me in the right direction.