I have a habit of prepending ‘time’ to all of my ‘make’ commands in order to keep a rough estimate of how long build jobs take.

Adhering to this custom, I performed a ‘make’ command on a project that didn’t actually require any rebuilding. So how does the following happen?

$ time make -j5

[...]

real    1770m35.893s
user    0m12.408s
sys     0m11.692s

Answer: The machine (virtual machine, actually) had just been started, had a grossly out-of-sync clock, and must have synced to the time server during that narrow window that the build was occurring:

make[2]: Warning: File `...' has modification time 1.8e+04 s in the future
make[2]: warning:  Clock skew detected.  Your build may be incomplete.