Its a 24 hour clock 0001 should get you one minuite past midnight and 1301 should get you 1:01 pm. You can see in the construction script of BP skydome DefaultHour which is probably the hour your playing with is clamped between 0.0f and 24.0f (then multiplied by 60.0f to get currentMinute)
If youd like some more information on the ToD system search for what it was built off search for “Gregdumb’s time-of-day skydome blueprint, version 1.2! Created with Unreal Engine 4.2.1.”