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[[File:Sundial-egypt.jpg|thumbthumbnail|250px|left|Figure 1. The oldest sundial found, although these objects are probably more ancient, derives from Egypt from the 2nd millennium BCE.]]
The basic units we use to save time have not significantly evolved, showing their ancient historical roots. Timekeeping developed in early recorded history, with different societies using their natural surroundings and devices they created to help keep track of time. The keeping of time was essential to early agriculture, particularly in irrigation, where timing access to water was necessary. Increasingly, timekeeping was not just conducted by the select few by much of society.
==Early Timekeeping Devices==
[[File:Salisbury Cathedral clock-1060x450.jpg|thumbthumbnail|left|250px|Figure 2. Perhaps the oldest known working clock is the clock in Salsbury cathedral, which dates to the late 14th century. ]]
Some of the earliest timekeeping devices involved the use of water, or what were called water clocks or <i>clepsydrae</i> as called by the Greeks. This involved either using outflow of water or inflow. Effectively, as water drained out or filled in, the rate was seen as relatively constant based on marking on containers that would then tell how much time had passed as the water drained or filled in. Such devices were known to have existed in many of the earliest complex societies in Eurasia, including in Egypt, Mesopotamia, the Indus, China, and likely other regions, including ancient Greece and Rome.
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[[Category:History of Science and Technonlogy]]
