That makes sense, but I'm getting a calculation error:

=IF(INDEX(Timesheet.vTime_in,ROW())<>"",
ADD(TIMEVALUE(INDEX(Timesheet.vTime_in, ROW())),9/24),"")

There aren't any syntax errors after I edit the formula and refresh, but the resulting calculation generates an error.

The division may be the issue. Try using 0.375 instead of 9/24.

It doesn't like that either.  Here's the syntax again...maybe I missed something:

=IF(INDEX(Timesheet.vTime_in,ROW())<>"",
ADD(TIMEVALUE(INDEX(Timesheet.vTime_in, ROW())),0.375),"")

The only thing I can think of is to check your variable names and/or add them to the formula again. I created a table with the exact same variable names (Timesheet and Timesheet.vTime_in) and pasting in your formula worked for me.

I double checked the variables and they are good.  When I pick a time from the drop-down list it doesn't appear to trigger the formula in the vTime_out field.  When I type a time and tab out of the vTime_in field, then it triggers the formula and shows the error.

I'm not sure what version of Forms everyone on this thread is using, but I couldn't get this to work with his formula either (I'm on 10.4.1.164).

I tried testing things out with both tables and independent fields and there seems to be some underlying issue with the way Forms is interpreting the Time variable.

If I do a formula like =ADD(0.5,0.375) or =ADD(0.5,TIME(9,0,0)) or =ADD(0.5,9/24)

It works every time.

However, as soon as I replace "0.5" with a time variable, everything falls apart and I get an empty result.

The only way I've been able to get this to work is with an additional "middleman" number field set equal to the first time value.

For whatever reason, converting the time to a decimal number first using this third field and referencing that instead allows the calculation to work to some degree.

First, I have a "Time_In" variable

Next, I have a "Time_Number" variable set equal to that time with 30 decimal places to ensure (hopefully) nothing gets cut off.

Then, in my "Time_Out" variable I add the hours to the numeric time instead of directly to the time variable and it works. 

=ADD(INDEX(Time_Table.Time_Number,ROW()),0.375)

But.... in the table it still doesn't recognize AM/PM when the time changes. Although the same approach works perfectly fine in independent fields.

=ADD(Time_Number,TIME(9,0,0))

However, if I switch the Time to 24 Hour, the table works as expected.

It really seems to me that there's some buggy behavior going on with the time fields, so you might just want to try JavaScript instead.

Time is a new-ish field type and it looks like there are still some wrinkles.

I'm on version 10.4.3.198, so perhaps it was fixed recently. Using an intermediary field is a good fix.

I'm on 10.4.1.164.  No idea how to do this in javascript so if there are some good examples you're aware of please advise.

Cool...I will try it out.

I updated it with my table name and column names using the variable names, but it doesn't seem to be doing anything.  I copy/pasted just the section of code that follows $(document).ready(function(){ since I have other code there for a calendar object.

// trigger when time in changes on any row of table
  $('.Timesheet').on('change','.vTime_in',function(){
    // get time value and am/pm value
    var t1 = $(this).find('input').val();
    var p1 = $(this).find('select').val();
    
    // convert values to moment.js time object
    var time = moment.utc(t1 + p1,'h:mm:ss A');
    
    // add 9 hours
    time.add(9, 'hours');
    
    // get new time and am/pm values
    var t2 = time.format('h:mm:ss');
    
    // need to use lowercase am/pm to match actual value attributes of am/pm options
    var p2 = time.format('a'); 
    
    // find time out field for current row
    var timeOut = $(this).parent('tr').find('.vFinal_out');
    
    // set time and am/pm values
    timeOut.find('input').val(t2).change();
    timeOut.find('select').val(p2).change();
  });