'Around the clock' is a race between the players, where each tries to catch the other one first.
First determine the starting number of the first player. The second player starts at the opposing number.
Example: P1 starts at 20, therefore P2 starts at 3.
Each player then alternately has 3 throws. Counting is done retroactively. The sum of all three throws determines the number of fields the player can move. Subsequently, a player can move at max 9 fields (3 triples).
Hitting the outter bull's eye adds -1 to the player's movement.
Hitting the inner bull's eye switches the players locations.
The player who first lands exactly on the other's current number wins. This is true for any direction, i.e. moving forwards or backwards.
If a player doesn't land exactly, the player has overthrown. The game still contiues, but the one who overthrow is now most likely very close in front of the other player, becoming an easy target.