JsPHP: a JavaScript library providing the PHP API

function idate (format, timestamp) {
    // http://jsphp.co/jsphp/fn/view/idate
    // +   original by: Brett Zamir (http://brett-zamir.me)
    // +      input by: Alex
    // +   bugfixed by: Brett Zamir (http://brett-zamir.me)
    // +   improved by: Theriault
    // +  derived from: date
    // +  derived from: gettimeofday
    // *     example 1: idate('y');
    // *     returns 1: 9
    if (format === undefined) {
        throw 'idate() expects at least 1 parameter, 0 given';
    }
    if (!format.length || format.length > 1) {
        throw 'idate format is one char';
    }

    // Fix: Need to allow date_default_timezone_set() (check for this.php_js.default_timezone and use)
    var date = ((typeof timestamp === 'undefined') ? new Date() : // Not provided
    (timestamp instanceof Date) ? new Date(timestamp) : // Javascript Date()
    new Date(timestamp * 1000) // UNIX timestamp (auto-convert to int)
    ),
        a;

    switch (format) {
    case 'B':
        return Math.floor(((date.getUTCHours() * 36e2) + (date.getUTCMinutes() * 60) + date.getUTCSeconds() + 36e2) / 86.4) % 1e3;
    case 'd':
        return date.getDate();
    case 'h':
        return date.getHours() % 12 || 12;
    case 'H':
        return date.getHours();
    case 'i':
        return date.getMinutes();
    case 'I':
        // capital 'i'
        // Logic derived from getimeofday().
        // Compares Jan 1 minus Jan 1 UTC to Jul 1 minus Jul 1 UTC.
        // If they are not equal, then DST is observed.
        a = date.getFullYear();
        return 0 + (((new Date(a, 0)) - Date.UTC(a, 0)) !== ((new Date(a, 6)) - Date.UTC(a, 6)));
    case 'L':
        a = date.getFullYear();
        return (!(a & 3) && (a % 1e2 || !(a % 4e2))) ? 1 : 0;
    case 'm':
        return date.getMonth() + 1;
    case 's':
        return date.getSeconds();
    case 't':
        return (new Date(date.getFullYear(), date.getMonth() + 1, 0)).getDate();
    case 'U':
        return Math.round(date.getTime() / 1000);
    case 'w':
        return date.getDay();
    case 'W':
        a = new Date(date.getFullYear(), date.getMonth(), date.getDate() - (date.getDay() || 7) + 3);
        return 1 + Math.round((a - (new Date(a.getFullYear(), 0, 4))) / 864e5 / 7);
    case 'y':
        return parseInt((date.getFullYear() + '').slice(2), 10); // This function returns an integer, unlike date()
    case 'Y':
        return date.getFullYear();
    case 'z':
        return Math.floor((date - new Date(date.getFullYear(), 0, 1)) / 864e5);
    case 'Z':
        return -date.getTimezoneOffset() * 60;
    default:
        throw 'Unrecognized date format token';
    }
}