Way back in the 1850's the trip from England to Melbourne was by slow sailing ship (the fastest clippers took about 70 days). The ships took a Great Circle path (a straight line on a globe). They would go down the coast of Africa until they hit the South Pole, turn left (trying to miss as many icebergs as possible) travel a bit further, turn left up towards Victoria. They passed through "The Eye of the Needle" - the gap between Cape Otway and King Island. This is 90km wide. Accurate navigation was required to make a successful voyage. As remarked by the numerous wrecks along both coasts, this was a problem.
Two numbers are required to fix your position on the surface of this globe - Latitude and Longitude.(sound familiar?)
For centuries navigators have been able to find their Latitude (how far North or South of the equator), using Octants and Sextants, but Longitude was a big problem. It was finally solved by Mr. Harrison around 1740. He designed (and built) accurate seagoing clocks. To tell your Longitude all you needed was Greenwich Mean Time and your local time.
So the clock (and its accuracy) became a very important piece of navigational equipment. Unfortunately ships and the sea are not good for clocks, so what the navigator did that every time he made landfall, he would adjust his clock to minimise his positional error.
So every where that was settled, we built an Observatory. To tell time accurately you needed a large transit telescope. The way we conveyed the time information from the Observatory to the ships was using the Timeball Tower (you knew I was going to get there eventually, didn't you).
Just before 1pm each day the ball was raised up the tower and exactly at 1:00pm dropped. The navigators, watching from their locations in dock, would then adjust their clocks.
Feel lucky you have a GPS?