In the diagram here for 2002 ranger radio: http://www.therangerstation.com/tech...dio_Wiring.pdf
It looks like fuse #29 would be the clock fuse and the light green/violet striped wire is the full time power on the back of the radio.
Clock needs power 24/7 to stay correct, this power is also used to hold radio preset stations in memory.
When the clock comes on for that half second is it the correct time or does it show 12:00?
If time looks correct then issue is IN the radio itself, not a power or ground issue.
Air bag light is probably not related, outside of it having a connection that is effected by hitting the dash, which most likely would be in the switch, and probably won't cause you any problems if you stop hitting the dash :).
Airbag system and radio don't share any grounds or power connections