//This is completely ridiculous. var jan = new Date(this.getFullYear(), 0, 1).getTimezoneOffset(); var jul = new Date(this.getFullYear(), 6, 1).getTimezoneOffset(); var today = new Date().getTimezoneOffset(); if(jan == jul) { $('#daylight_savings').prop('checked', false); } else if(jan > jun) { //Northern hemisphere $('#daylight_savings').prop('checked', (jun==today)); } else { //jun < jan //Southern hemisphere $('#daylight_savings').prop('checked', (jan==today)); }