Easy as 1, 2, 3 (in base 5 + 5)

Two patterns:

       1234
       5678              01234
       9, 10              56789

(and hence some arithmetic:)

12 = 3 x 4
56 = 7 x 8
90 = 360/4

      0 + 12 = 3 x 4
      5 + 67 = 8 x 9 = 360/5

(in a minute there's 360/6 = 60 seconds)

4 x 5 x (6 + 6 + 6) = 360 = (5 + 5) x 6 x 6

                    1 + 2 + 3 + 4 = 5 + 5
1 + 2 + 3 + ... + 8 = 9 x 4 = 6 x 6

    1 + 2 + 3 + ... + (5 + 5) = 55
    1 + 2 + 3 + ... + (6 x 6) = 666