Calculate length of interview with start/end timestamps

Hi,
In my dataset downloaded from Kobo Toolbox, the timestamps for start/end of the interview look like this:
2021-04-13T16:21:56.639+05:45

I wanted to calculate the average length of the interviews. I have two questions:

  1. Is there a way that I can I use this timestamp format to calculate the length of the interview in Excel?
  2. For future surveys, would it work if I insert a calculate question with the following formula: ${end}-${start}

Regarding your first query:

Maybe this post discussed previously should help you solve your first query:

Regarding your second query:

Maybe this post discussed previously should help you calculate your survey time:

and this post too …