Event based

The reality is that kernel releases are event-driven, not time-driven. Which is good, as we'd have either thousands of brown-paper-bag releases or still be on version 1.x. Version dates are misleading, as the difference between two versions would yield no information on the number of events involved.

Now, one could argue that using events gives no indication of the time involved. However, when we talk of a kernel being "old" we don't been chronologically. What we mean is that the accumulation of time has resulted in a large enough change that the original is no longer tolerable.

It would, perhaps, be useful to increment by the number of significant kernel changes rather than by 1, at the cost of bloating the version number a bit. Gives more info, but only if there's a consensus on what is significant.

Chronological versioning, when the interval for a kernel is indeterminate (critical patches may come late and require several rounds of testing, for example, even for kernels with no user-significant changes), doesn't seem to tell you anything.