If I understand you correctly, I believe the soluntion would require custom JavaScript code.  Alternatively, this may or may not be a solution for you.

Every SharePoint list has the capability to create a comments field that appends to the list each time an item is edited.  It is achieved via the Multi-line text column and versioning.

To set this up open up your List Settings and turn on versioning in your list. 

Create a multi-line column (Comments) in your list and select the setting that says "Append Changes to Existing text".

Save. 

Now, whenever your user adds a comment, it is appended to existing comments with the users name and a date/time stamp.

Like I stated at first, this may not be the user experience you wanted, but it may get you close and doesn't require custom code.

If the user enters a comment and then selects "Add new row"

you can fullfil this requirement by writting your own trigger for Repeater Row Added event. within the trigger you can check whether a comment field has been entered and if so then set value for a date field

JavaScript events in Nintex Forms

or the form is saved

catching 'save' event might be a bit problematic.

I would two easier ways how to achieve similar outcome with less effort:

1. configure default value to current time for date control

2. populate date control from javascript within Repeater Row Added trigger as mentioned above.

it's not really 'save time' but might be close enough to meet your needs

Thanks everyone.

I was able to capture the date the comment was entered by adding a date control to the repeating section.

I set the date control default to "today".

I then created two rules on the date control:

• if the comment field is null or empty - "hide".
• if the comment field is not null or empty - "disable."

I have tested this and each date is captured and retained when the date control is disabled.

No need to create a list column for the date control or associate it to anything. The date is captured in the repeating control xml.

Not exactly what I was looking for (I didn't want to see the control, wanted to use a calculated value so I can control the text visually) but this prevents me from having to insert any custom code.

Bill

I had the similar requirements,Please go through the link Repeating Conrol + Current user Name + Time .I did the same functionality