A 'Jiffy' Is a Real Unit of Time (Sort Of)

Next time someone promises to be there "in a jiffy," you could technically ask them to be more specific. Is that 1/100th of a second? 1/60th? Or are we talking about the time it takes light to travel one centimeter? Because a jiffy is genuinely a unit of scientific measurement—it's just that nobody can quite agree on how long it is.

The Word Scientists Couldn't Resist

The phrase "in a jiffy" has been bouncing around English since at least the 1780s, meaning simply "in a moment" or "very quickly." Nobody knows exactly where it came from—some linguists suspect it might be thieves' slang, others think it could be related to the word "gliff" (a brief glimpse).

But here's where it gets fun: scientists loved the word so much they decided to make it official. The problem? Different fields defined it differently.

Pick Your Jiffy

Depending on who you ask, a jiffy equals:

• In computing: Typically 1/100th of a second (10 milliseconds), though some systems use 1/60th of a second
• In electronics: The time between alternating current cycles—1/60th of a second in North America, 1/50th in Europe
• In physics: The time it takes light to travel one fermi (about 3 × 10⁻²⁴ seconds)—essentially the blink of a subatomic eye
• In chemistry: The time it takes light to travel one centimeter (about 33.3 picoseconds)

So when a physicist says "jiffy," they mean something unfathomably shorter than when a computer programmer says it.

Why Computers Care About Jiffies

In the world of operating systems, a jiffy is genuinely useful. It's the interval between system timer interrupts—basically, how often your computer's internal clock "ticks." Linux systems famously use jiffies to measure time intervals, schedule tasks, and keep everything running smoothly.

The exact length varies by system configuration, but 100 jiffies per second (or 100 Hz) became a common standard. This means your computer is counting jiffies right now, thousands of times per minute, keeping your digital world synchronized.

The Phrase Came First

Here's the twist that makes this fact slightly less mind-blowing but more linguistically interesting: the casual phrase predates all the scientific definitions by about 150 years. Scientists didn't discover an existing unit called a jiffy—they borrowed a fun word from everyday English and gave it precise meanings.

It's a bit like if physicists had decided to define "a hot second" as exactly 47 milliseconds. The phrase existed first; the measurement was retrofitted onto it.

So the next time you promise to do something "in a jiffy," you're either pledging to complete it in 10 milliseconds, 33 picoseconds, or an amount of time so small that light barely has time to cross an atomic nucleus. Best to just say "soon" if you want to be accurate.