Increase Time in 8 hours Intervals

Hello @graicifyd

You can insert an “HTML Content” field in the form, and enter the following piece of code as its content:

<script>
fbuilderjQuery(document).one('formReady', function () {
    getField('fieldname2').setVal(GETDATETIMESTRING(DATETIMESUM(getField('fieldname1').val(true, true), 'mm/dd/yyyy hh:ii', 8, 'h'), 'mm/dd/yyyy hh:ii'));
});
</script>

Note I assumed the date/time format of your fields is mm/dd/yyyy hh:ii

Best regards.