The clepsydra was first invented around the time of 15th century BC. clepsydras were named after the Greeks. These objects appeared to have a container with a small hole in it’s bottom where water would seep through at a constant pace. The drip-drop of the water would be later what the tick-tock in clocks is now. These water clocks had marks on the outside that indicated hours. The time was dependent on the increase or decrease of water which filled the inside of the drum. The lines on the outside were different sizes so that they could accommodate the shorter length of hours in the winter than in the summer. The clepsydra was not used to measure hours but rather used to measure time allotted for a particular event. Clepsydras were used during the sunlit day, however no evidence has proven that this same device was used during the night.