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How do computers keep time?

My first laptop lost track of time, so that got me thinking: how do computers keep track of time? Can they do it forever? And why don't they lose track of time when we turn them off?

Turns out the answer is a combination of processor, quartz crystal and the internet. They all work together to keep time.


This video wouldn't be possible without the work of others. Here are the sources I've used during my research & script writing:

Apple II system clocks. (n.d.). Wikipedia.
Clock Interrupt. (2009, November 1). Microsoft.
Clock Speed. (2017, May 22). TechTerms.
Hertz. (n.d.). Wikipedia.
How do computers keep track of time? (2016, March 25). StackExchange.
Infographics: Operation Costs in CPU Clock Cycles. (2016, September 12).
Jackson, J. (2015, March 2). Why computers still struggle to tell the time. PCWorld.
Network Time Protocol. (n.d.). Wikipedia.
Nonvolatile BIOS memory. (n.d.). Wikipedia.
Quartz clock. (n.d.). Wikipedia.
Real-time clock. (n.d.). Wikipedia.
Schmidt, B. (2015, December). CPU Clocks and Clock Interrupts, and Their Effects on Schedulers. Accu.
ThunderClock Apple IIe MouseDesk UniDisk 3.5 and SCSI Drive. (2017, July 11). VintageGeek.
ThunderClock Plus - Parts List, Layout, Schematics. (n.d.).
Woodford, C. (2018, April 29). Quartz clocks and watches. Explain that stuff.
Year 2000 problem. (n.d.). Wikipedia.
Year 2038 problem. (n.d.). Wikipedia.