Descent from FL370 to FL80 is through 29,000ft and at 1,800ft/min this will take 16.1 minutes.  

In 16.1 minutes the aircraft will cover 62.3nm at its ground speed in the descent of 232kts.  

At 0422 distance to run to top of descent is 184 – 62.3 = 122.7nm and at cruise ground speed of 320kts this will take 23 minutes.  

Commence descent at 0422 + 23min = 0445.