Swift NSDateFormatter timezone not working

Question

I'm am trying to convert a date string to NSDate format, but I'm not getting the correct results. I want NSDateFormatter to ignore everything to do with timezones and just use the Europe/Amsterdam timezone, regardless of the timezone set int the date string, since it's going to be an app for people within this timezone only.

My script:

func convertDate(dateStr: String) -> NSDate?{
    var dateFormatter = NSDateFormatter()
    dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ssZZZZZ"
    dateFormatter.timeZone = NSTimeZone(name: "Europe/Amsterdam")

    var date = dateFormatter.dateFromString(dateStr)
    if (date != nil) {
        return date
    } else {
        var dateFormatter = NSDateFormatter()
        dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss"
        dateFormatter.timeZone = NSTimeZone(name: "Europe/Amsterdam")

        date = dateFormatter.dateFromString(dateStr)
        if (date != nil) {
            return date
        }
    }

    return nil
}

I use this function to convert a date to NSDate format, the date can be 2 formats, either the first one or the last one, so that's why I implemented this simple check.

Input string: 2015-09-07T12:48:00+0200
Output date: 2015-09-07 10:48:00 +0000

Input string: 2015-09-07T10:35:00
Output date: 2015-09-07 08:35:00 +0000

Input string: 2015-09-07T14:40:00
Output date: 2015-09-07 12:40:00 +0000

The dates are always 2 hours behind for some reason.