Countdown to the Next Century Screensaver
The Countdown to the Next Century screensaver counts down the real time remaining until January 1, 2100. It is free, runs in your browser, and ESC exits.
Live preview
Press ESC to leave fullscreen. Settings are saved in your browser only.
How the Countdown to the Next Century screensaver works
The saver computes the real exact difference between the current moment and January 1, 2100 at midnight.
Days, hours, minutes and seconds all tick down live, recalculated every frame.
The computation runs entirely in your browser — no network fetch is needed.
It is a pure calendar calculation, accurate down to the second.
Why 2100 is a calendar oddity
The year 2100 is a small trap built into the Gregorian calendar. The usual rule says a year divisible by four is a leap year, but century years are exempt unless they are also divisible by 400. That is why 2000 had a February 29 and 2100 will not. Pope Gregory XIII’s reform of 1582 introduced the rule to stop the calendar drifting against the seasons, and 2100 will be the next century year to skip the extra day, after 1900.
There is also an argument over whether January 1, 2100 starts a new century at all. Because the counting of years has no year zero, the 21st century strictly runs to the end of 2100, and the 22nd begins in 2101. Popular usage tends to celebrate round numbers instead, which is why many people marked the year 2000 as the new millennium while pedants insisted it began a year later.
A countdown like this is an arithmetic exercise on the calendar rather than a physical measurement. Leap years in between are counted correctly, but the display follows whatever clock and time zone your device uses, so the zero moment depends on where you are.
A worked example
As each real second passes, the seconds digit rolls over, and every so often a full day quietly drops off the remaining count.
Settings & tips
- Accent recolours the countdown digits.
- A fun long-range novelty countdown, not a practical deadline.
- No internet connection is required — the math runs locally.
Frequently asked questions
- Is this a real calculation?
- Yes — it computes the real exact time remaining until January 1, 2100.
- Is a key needed?
- No — it is a pure local calculation.
- Is it free?
- Yes — free, no download, in your browser.
- Will I still be watching when it hits zero?
- Almost certainly not — that is rather the fun of it.
- Is 2100 a leap year?
- No. It is divisible by 100 but not by 400, so February 2100 has 28 days under the Gregorian rules.
- Does the countdown include leap seconds?
- Computer clocks generally ignore leap seconds, so the countdown follows ordinary calendar time rather than atomic-time corrections.
- Is the 22nd century really starting on that date?
- Strictly, no. There was no year zero, so centuries are counted as 1 to 100, and the next one begins in 2101, even though 2100 looks like the natural boundary.