Calculating Date/Timer Differences Dynamically

This one might be good to pre-calculate as a column, if your logic never changes. Below is a DAX column expression that seems to work. Not sure how much data you have, but reply back if it is not performant and there may be a better way to write it. It returns the time in minutes as a decimal. It is best to keep durations as a decimal and format it later to mm:ss in your visuals if needed (you can't add up text strings, so not good to convert it yet). This could be adapted to be a measure but it may not be performant and whether it worked or not would depend on the fields used.

ResponseTime (minutes) =
VAR SubDT = Quotes[Submission Date]
VAR ThisResponse = Quotes[Response Date]
VAR ResponsesThisQuoteVersion =
    CALCULATETABLE (
        DISTINCT ( Quotes[Response Date] ),
        ALLEXCEPT ( Quotes, Quotes[Quote Number], Quotes[Quote Version] )
    )
VAR MinResponse =
    MINX ( ResponsesThisQuoteVersion, Quotes[Response Date] )
VAR PreviousResponse =
    MAXX (
        FILTER ( ResponsesThisQuoteVersion, Quotes[Response Date] < ThisResponse ),
        Quotes[Response Date]
    )
RETURN
    IF (
        MinResponse = ThisResponse,
        ThisResponse - SubDT,
        ThisResponse - PreviousResponse
    ) * 24 * 60

Calculate and Format Durations in DAX – Hoosier BI

Pat