If you've ever found yourself confused when a colleague tells you they were born in the late '90s (how are they even old enough to be working?!), or wondering how it can possibly be summer already when we've only just had Christmas, then good news -- you're not alone.

Time, as Stephen Hawking taught us, is a strange concept. And the older you get, the more confusing it seems to become.

This is something that's actually been studied. There's a psychological concept known as Weber's Law, for instance, that deals with how our perception of something will change based on its size, or quantity. As mathematician and presenter Hannah Fry shows in this Numberphile video, the law can be applied to time, too. The more years you've experienced on this earth? The more quickly additional years seem to fly by.

(Okay, so it's a little bit more complicated than that, but that's the TL;DR version, anyway.)

Basically, time -- and our changing perception of it -- is a tad bonkers.

Which brings us to this viral tweet from Twitter user @quartzen. The tweet was posted on Monday, and it seems to have led Twitter down something of a rabbit hole...

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At the time of writing, that's been retweeted over 5,500 times. Judging by the reactions, it clearly touched a nerve.

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Perhaps it's something to do with fact the year 2000 was such a big milestone, but it doesstill seem fairly recent, right?

Although if the responses to the original tweet tell us anything, it's that everyone's perception of time is clearly quite different...

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...and the concept of a new decade is very difficult to comprehend.

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It clearly isn't just millennials who feel confused by time, either.

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You know what'll be reallyweird? One day, as we start edging closer and closer to 2100, being born in the previous millenniumwill start become a thing of note.

Hopefully we'll still have Twitter then, so we can at least continue to find peace in our shared bafflement.