I want people to be able to tell how much they have worked during their shift and this seems like a perfect solution. There is just one problem. They can also work till the next day (ie: from the 5th 20:00 to 6th 04:00). The labels within the slider (9:00 and 18:00) are not a must and I don't think 00:00 till 48:00 would look visually appealing.
What would be the best way to do this keeping the obviousness for the user? Should I even use a slider for this?