Hi Tableau Champs out there

I'm struggling with something that you probably have a solution for it.

I have a data source with milestones per day that are reached, means for every day I have multiple records (for each milestone one) with ID of the milestone, a field for date (only date) and and time (HH:mm).

I want to show a trend graph (line) per day (on x-axis) and by hour (on y-axis), which is a quite easy thing. It looks like that:

Now, I want to have a custom sort on Y-Axis, means I want to start the Y-Axis at 20:00 to 24:00 (resp: 0:00) and then go one with 0:00 to 19:00, because it's an overnight procedure.

I have found a way by creating a calculated field, but the issue is that I have now numbers on the Y-Axis as label and I need to display hours.