Once(now()) gives 2 date formats from different tablets

Hello everyone. I hope you are doing well.
Recently i wrote a form and my clients wanted to know how much time did it each respondent spend on different parts of the questionnaire. and i used the syntax below where for example after a respondnt selected a choice at br2 ts3 would calculate a timestamp. everything was going fine and data was coming in this format: dd-mm-yyyy hh:mm:ss

But i saw that yesterday the data coming from one my interviewers who was using a different tablet other than the other interviewers came in this format: dd-mm-yyyy.
But i need the hh:mm:ssto measure the timestamp. please does anyone know why does this happend and any solution for this?

or do you know ny other way to measure timestamps
select_one BR1 BR2 “BR2. Cila është banka …” selected(${BR1},filter) yes
calculate end_timestamp3 TS3 if(${BR2}!=‘’,once(now()),‘’)

@ricard99, maybe this post discussed previously should also help you get some insights …

And this post too …