I was working on figuring out the uptime for one of our services at work. The service was down for 96 minutes. Our uptime only counts for the duration that people are actually doing work in the office, which works out to a convenient 40 hours.

I do the calculations, and it turns out that 96 minutes of downtime during a 40 hour period works out to be 96 percent uptime?! I’ve tried plugging some other numbers, but they don’t seem to work out so cleanly!

Am I missing something? Should this be expected behaviour?? Please, let me know!

My work is as follows,

t = new Date("2026-06-17 14:42:00");
// 2026-06-17T14:42:00.000Z
u = new Date("2026-06-17 16:18:00");
// 2026-06-17T16:18:00.000Z
u - t;
// 5760000    time passed in milliseconds
(u - t) / 1000;
// 5760       bring that down to seconds
(u - t) / 1000 / 60;
// 96         bring that down to minutes
(u - t) / 1000 / 60 / 60;
// 1.6        bring that down to hours
40-1.6;
// 38.4       get the total uptime
38.4/40;
// 0.96       get the percentage of uptime