Hourglasses serve as timekeeping instruments, utilizing the flow of sand from one glass container to another to measure intervals.

In the Western tradition, an hourglass typically comprises two glass spheres connected by a narrow tube.

The passage of time is gauged by the duration it takes for the sand-filled upper sphere to trickle through the narrow channel into the lower globe.

These timepieces have a nominal run time of around 1 minute, after which they can be inverted to restart the time measurement process.

Several factors influence the accuracy and functionality of an hourglass. The quantity of sand, the curvature of the glass bulb's interior, the width of the neck tube, and the type and quality of the filler all contribute to the instrument's timekeeping precision.

It's worth noting that there is a subtle difference in timekeeping between an hourglass in the forward and inverted position, owing to the shape of the curve inside the glass bulb.

Before the advent of clocks, various timekeeping methods existed, with hourglasses being just one of them. Sundials, copper kettle drips, and even incense were employed to measure time. Sundials, in particular, played a crucial role, serving as the reference for all timekeeping instruments during the winter and summer solstices.

The hourglass, however, is not a tool to indicate the exact moment; instead, it is a timekeeping device akin to a stopwatch in the hands of a race referee. It does not display the current time but aims to set limits on tasks within a predefined timeframe.

For instance, if an hourglass is designated to run out twelve times a day and night, it can be used to gauge an hour or a few hours, with someone monitoring it, turning it upside down, and recording each completion.

An alternative to the hourglass, known as the "leaky pot" or carved hourglass, adheres to the isochronous principle of drip timekeeping. It comes in two types: drain and water. The drain type employs special containers to record water leak time, while the water type features a bottom-sealed container, measuring the time it takes to fill up with water.

Early engraved funnels were predominantly of the draining type, with water leaking from the bottom side of the funnel pot. Later improvements led to the water type, ensuring a constant water flow into the pool and enhancing timekeeping accuracy.

Sundials, like hourglasses, function as tools to indicate time. Basic sundials are effective during the day, relying on the sun's position, but their accuracy diminishes during the night, except on the full moon. However, due to the moonrise time delay of approximately 48 minutes per day, the sundial may deviate from actual time by this increment.

Advanced sundials include charts for calculating corrections and dials for adjusting latitude and longitude, ensuring more precise time indications.

The concept of timekeeping through ingenious devices extends beyond hourglasses. Water clocks, also known as clepsydra, were used in ancient civilizations such as Egypt and China. These clocks employed a regulated flow of water to measure time intervals.

The inflow or outflow of water was controlled by the size of an aperture, ensuring a consistent rate of timekeeping. Additionally, candle clocks were prevalent in medieval times, with marked increments on the candle indicating the passing hours.