Hourglasses, also known as sandglasses or sand timers, were first used in the 14th century, although it is unclear exactly when they were invented. The earliest written reference to an hourglass dates back to the early 14th century in Europe, but they may have been used earlier in other parts of the world. Hourglasses were used as a reliable way to measure time, especially for tasks that required precise timing such as navigation at sea, cooking, and scientific experiments.