I would suggest making a Tag with the type of ‘Date’ that stores the time of the last transition from 1->0.
Then in your Boolean tag, write a tag-changed event script that reads:
if previousValue.value == 1 and currentValue.value == 0:
system.tag.write("Path_to_date_tag", system.date.now())
So now you’ve got the time of that change. In your vision window to display the duration to the user, in an expression binding do something like:
secondsBetween({datetag}, now())
Which will display the raw integer seconds since the last 1->0 change. You could format that into a string as you like.