window.bdayCal = function () {
    var cbs = document.querySelectorAll('#birthday-grid-c1d2 input:checked');
    if (!cbs.length) {
        alert('Select at least one person first.');
        return;
    }

    var yr = new Date().getFullYear();

    // Start ICS file
    var ics =
        'BEGIN:VCALENDAR\n' +
        'VERSION:2.0\n' +
        'PRODID:-//Boser-Herman//EN\n';

    // Add events
    cbs.forEach(function (cb) {
        ics +=
            'BEGIN:VEVENT\n' +
            'SUMMARY:' + cb.getAttribute('data-n') + "'s Birthday\n" +
            'DTSTART;VALUE=DATE:' + yr + cb.getAttribute('data-d') + '\n' +
            'DTEND;VALUE=DATE:' + yr + cb.getAttribute('data-d') + '\n' +
            'RRULE:FREQ=YEARLY\n' +
            'END:VEVENT\n';
    });

    // Close ICS
    ics += 'END:VCALENDAR';

    // Download file
    var a = document.createElement('a');
    a.href = URL.createObjectURL(new Blob([ics], { type: 'text/calendar' }));
    a.download = 'boser_herman_birthdays.ics';
    a.click();
};