Date.prototype.setISO8601 = function(dString) {
    var regexp = /(\d\d\d\d)(-)?(\d\d)(-)?(\d\d)(T)?(\d\d)(:)?(\d\d)(:)?(\d\d)(\.\d+)?(Z|([+-])(\d\d)(:)?(\d\d))/;
    if (dString.toString().match(new RegExp(regexp))) {
        var d = dString.match(new RegExp(regexp));
        var offset = 0;
        this.setUTCDate(1);
        this.setUTCFullYear(parseInt(d[1], 10));
        this.setUTCMonth(parseInt(d[3], 10) - 1);
        this.setUTCDate(parseInt(d[5], 10));
        this.setUTCHours(parseInt(d[7], 10));
        this.setUTCMinutes(parseInt(d[9], 10));
        this.setUTCSeconds(parseInt(d[11], 10));
        if (d[12])
            this.setUTCMilliseconds(parseFloat(d[12]) * 1000);
        else
            this.setUTCMilliseconds(0);
        if (d[13] != 'Z') {
            offset = (d[15] * 60) + parseInt(d[17], 10);
            offset *= ((d[14] == '-') ? -1 : 1);
            this.setTime(this.getTime() - offset * 60 * 1000);
        }
    }
    return this;
}

Number.prototype.toRad = function() {
    return this * Math.PI / 180;
}

function haversine(lat1, lat2, lon1, lon2) {
    var R = 6371; // km
    var dLat = (lat2 - lat1).toRad();
    var dLon = (lon2 - lon1).toRad();
    var a = Math.sin(dLat / 2) * Math.sin(dLat / 2) +
            Math.cos(lat1.toRad()) * Math.cos(lat2.toRad()) *
            Math.sin(dLon / 2) * Math.sin(dLon / 2);
    var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
    return R * c;
}

Array.prototype.max = function() {
    return Math.max.apply({}, this)
}

Array.prototype.min = function() {
    return Math.min.apply({}, this)
}

Array.prototype.sum = function() {
    for (var i = 0, sum = 0; i < this.length; sum += this[i++]);
    return sum;
}