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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.

Sources

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

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Apple II system clocks. (n.d.). Wikipedia. https://en.wikipedia.org/wiki/Apple_II_system_clocks
Clock Interrupt. (2009, November 1). Microsoft. https://social.microsoft.com/Forums/en-US/11ae5810-cb78-42a3-9761-efa3e8455993/clock-interrupt?forum=kernel
Clock Speed. (2017, May 22). TechTerms. https://techterms.com/definition/clockspeed
Hertz. (n.d.). Wikipedia. https://en.wikipedia.org/wiki/Hertz
How do computers keep track of time? (2016, March 25). StackExchange. https://cs.stackexchange.com/questions/54933/how-do-computers-keep-track-of-time
Infographics: Operation Costs in CPU Clock Cycles. (2016, September 12). http://ithare.com/infographics-operation-costs-in-cpu-clock-cycles/
Jackson, J. (2015, March 2). Why computers still struggle to tell the time. PCWorld. https://www.pcworld.com/article/2891892/why-computers-still-struggle-to-tell-the-time.html
Network Time Protocol. (n.d.). Wikipedia. https://en.wikipedia.org/wiki/Network_Time_Protocol
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Quartz clock. (n.d.). Wikipedia. https://en.wikipedia.org/wiki/Quartz_clock
Real-time clock. (n.d.). Wikipedia. https://en.wikipedia.org/wiki/Real-time_clock
Schmidt, B. (2015, December). CPU Clocks and Clock Interrupts, and Their Effects on Schedulers. Accu. https://accu.org/index.php/journals/2185
ThunderClock Apple IIe MouseDesk UniDisk 3.5 and SCSI Drive. (2017, July 11). VintageGeek. https://vintagegeek.wordpress.com/2017/07/11/thunderclock-apple-iie-mousedesk-unidisk-3-5-and-scsi-drive/
ThunderClock Plus - Parts List, Layout, Schematics. (n.d.). http://comp.sys.apple2.narkive.com/FfThN9ci/hardware-clock-thunderclock-plus-parts-list-layout-schematics
Woodford, C. (2018, April 29). Quartz clocks and watches. Explain that stuff. https://www.explainthatstuff.com/quartzclockwatch.html
Year 2000 problem. (n.d.). Wikipedia. https://en.wikipedia.org/wiki/Year_2000_problem
Year 2038 problem. (n.d.). Wikipedia. https://en.wikipedia.org/wiki/Year_2038_problem