Days are 86,400 seconds long
False. Even if you live in a place that doesn’t have Daylight Saving Time, you are still subject to rogue leap seconds that get inserted into our calendars every now and then. If you care about being precise, you care about leap seconds. And if you’re writing software for others to use, chances are at least one of your users will be affected by DST at some point.
Days are 24 hours long
False. Many places around the world observe Daylight Saving Time, which means that people living in these locations will sometimes experience 23 hour days (when they “leap forward”) and 25 hour days (when they “leap back”).
... read the whole story at yourcalendricalfallacyis.com.