Ok I understand. In Airtable, Duration is not the “Time” part of a DateTime, it is really just a “Duration”.
To do what you are asking for, you have to set an intermediate field that will calculate the corresponding DateTime.
Create a new Formula field formatted as DateTime DATEADD(TODAY(), Duration, 'seconds')
This will create a “today” date with time = 00:00 then add the Duration to it
Convert this DateTime to a String DATETIME_FORMAT(DateTime, "hhmm")
This result can actually be achieved using a one line formula : DATETIME_FORMAT(DATEADD(TODAY(), Duration, 'seconds'), "hhmm")
Please tell me if this fit your needs.
If it does work on your side, please mark this reply as an answer :slightly_smiling_face: