It used to be that a major version bump for a major program was a major event. Major versions usually introduce new features and make other changes that cause incompatibilities. Big companies have to test and plan before deploying them. Those were the days.

Now, for many of us, our Web browser is the most important application we use and that stability has been taken away from us. Google Chrome has been on a major version tear since its 1.0 release in December 2008. Since then, it has skyrocketed to the current version of 16.0.912.77 and is due to hit 17 any day now.

But Mozilla is somehow more disturbing in the disdain with which its treats IT managers. This week saw the release of Firefox 10.0, the latest in a regular series of major releases. The 3.x generation was long-lived. It was released in June 2008 and 4.0 didn't come out till March 2011. But since then Mozilla has actually outpaced Google, committing to a schedule of major version updates every six weeks. Because of this, we know that Firefox 11 will be released on March 16, 2012. (This will also be Patch Tuesday for Microsoft and perhaps Adobe. Oy.)

The lone concession Mozilla has made to those who don't want to get on their version update hamster wheel is that they have kept the 3.x generation available and are providing security updates for it. But if you want any modern browser features, you need to adjust your schedule to Mozilla's. They won't even provide a managed install version, which at least Google does with Chrome.

Where is this all going? We'll tell you where. We did the math.

The version growth rate for Firefox is easy to calculate. You get a new one every six weeks. But the last seven versions of Chrome have been released, on average, every six and two-third weeks. Firefox is behind in version numbers, but releasing at a more rapid clip. The gap leads inexorably to the important question: When will the two have the same version?

The answer is plotted below and you can right click here to save the link for our Excel spreadsheet with the data.

If current trends persist, on Feb. 5, 2019, Mozilla will release version 71.0 of Firefox, matching the then-current major version of Google Chrome. And March 2, 2021 is when Firefox finally gains clear separation at version 89.

We're looking only at major versions, so you'll notice the curve is not a straight line, but a series of steps. Along the horizontal portions of the curve there will be minor version releases, generally for security updates.

There. Now at least you can do some planning. Mark your calendars.

Ben Gottesman provided actuarial consulting for this story.