The engineer behind Brick Technology, who previously built pneumatic LEGO engines that ran on compressed air, constructed a solar-powered mechanical LEGO clock that keeps time for one billion years.
The clock has dials to display seconds, minutes, hours, days, weeks, months, years, decades, centuries, millenia, mega-annums and galactical years (time required for the Sun to orbit once around the centre of the Milky Way Galaxy).
They also explain how the clock was constructed and how it keeps time.
The first component resembles a grandfather clock with a weight-driven pendulum anchor escapement. The escapement wheel rotates 1 tooth per second. Different gear trains transmit motion from the escapement to all complications from days to years to decades. As soon as the weight touches the ground, a rewinding motor is triggered to raise the weight and “recharge the clock”. This happens every 2 minutes.