getting a power outage warning letter from the city before a "scheduled grid upgrade" and now im shopping for a UPS

So the city mailed me a notice saying theyre cutting power to my whole block next Thursday from 9 to 3 for "infrastructure modernization." The notice showed up on Tuesday, so I got about a week and a half Theres no explanation of what theyre modernizing It just says residents are "encouraged to make arrangements"... which sounds nice until you remember last time they did this it went two hours over and nobody ever heard a word about it Anyway that got me thinking I should probably have a battery backup on the desktop i've got a family member who keeps a file server running in the basement too, so I'm guessing everyone here already has one and I'm late as usual. Do I actually need a pure sine wave unit or is that just marketing? I've got a 750w psu with active PFC, and I keep reading different answers depending on who's selling what. I mostly want enough time to save stuff and shut down properly, not run the thing all afternoon. Also the power coming back on will reset every clock in the house except the one on my wrist. Which I'll point out to anyone who'll listen...