The clock is regarding one of the oldest human inventions, where it’s meeting the need to measure the time in the natural units, such as second, minute, day, month and the year. However, if you want to measure the time accurately, you’ll need the help of some devices.
Brother Paul has invented the first record of a minute hand on a clock in 1475. Alexander Bain, a Scottish clockmaker was the first inventor that patented the electric clock in 1840! Although the digital clock is one of the most common items in nowadays, but you cannot miss this digital clock:

Digital clock date thermometer [In time/date/temp mode: display time 14:32]

It is a small adjustable clock/date with thermometer function based on PIC16F628 or PIC16F84 microchip and DS18S20 or DS18B20 temperature sensor. The hardware part is very simple because it only uses pic microcontroller, the DS18S20/DS18B20 sensor, 4x7 segments (common anode, something like KW4-301xxx Series, or common cathode something like CC56-21SURKWA), four transistors, some rezistors!

Note: Do not place DS18S20/DS18B20 near heat providers, best thing is to let it float in the air while is connected through isolated wires. See » How it works page for additional info.