#Ruby, 94

    puts (0..23).to_a.map{|h|?'+(h/2).to_s.rjust(2,?0)+?:+(h%2*30).to_s.rjust(2,?0)+?'}.join ",\n"

I tried golfing it with other methods but this ended up being the shortest one... it might be possible to golf it more but I don't have the time now.