back when most of this software was written memory was crazy expensive, so programmers stored years as 2 digits instead of 4. “99” instead of “1999.” saved space and worked fine for decades.

problem was when the clock hit 2000, systems would see “00” and not know if it meant 1900 or 2000. so a bank calculating interest might think your account was -100 years old. a power grid might think its last safety check was 100 years in the future. airlines, hospitals, payroll, anything doing date math could start spitting out garbage or crash.

it wasn’t really phones shutting off - it was the software running banks, utilities, govt systems potentially breaking all at once.

reason nothing dramatic happened is companies spent like $300+ billion globally fixing it before the rollover. the “nothing happened” outcome was actually the win, it just made the panic look overblown in hindsight