Show Time field with "HH:mm" format

Hi team,
I need to show in the time field only hours and minutes in the Sales Invoice(Posting Time field).
I tried

onload_post_render: function(frm) { 
             timeFormat: 'HH:mm',

but it seems the system cannot find field. It seems that Posting Time field is reloaded after onload_post_render hook. Can someone please check it also or give me some advices how to handle it. Thanks


Add one more field, read only small text or html so it can render time as per your requirement. momentjs is available.

Thank for your answer.