Toucan play at that game...

Every morning, at the same time, the parrots flew past the building site into the forest to hunt.  You can easily spot parrots because they always fly together in pairs.  Each afternoon, they flew back home.  Every day at the same time.  The workers started their jobs when the parrots went past on their way into the forest, and stopped when they were seen returning.

One afternoon the parrots were nowhere to be seen. The workers were vexed. They complained it was time to go home, but the boss just said 'Parrots na fly, you na go". They worked and worked until the sun went down.

The next day started as usual, but after half an hour the parrots were spotted on the horizon coming back from the jungle. The boss tried to stop them, but the workers just left. "Parrots fly, we go."

By the following morning, the boss had bought himself a watch.

(Thanks to Leonard for the story, and apologies to the world for the pun)