Neither the time executable from the GNU time package work completely correctly, nor does the GNU Bash built-in one.

tschwinge@flubber:~ $ \time sleep 2
0.00user 0.00system 9:38:00elapsed 0%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+0minor)pagefaults 0swaps
tschwinge@flubber:~ $ \time sleep 4
0.00user 0.00system 18:50:25elapsed 0%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+0minor)pagefaults 0swaps
tschwinge@flubber:~ $ \time sleep 6
0.00user 0.00system 28:00:53elapsed 0%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+0minor)pagefaults 0swaps
tschwinge@flubber:~ $ time sleep 2

real    0m2.093s
user    0m0.000s
sys     0m0.011s
tschwinge@flubber:~ $ time sleep 4

real    0m4.083s
user    0m0.000s
sys     0m0.010s
tschwinge@flubber:~ $ time sleep 6

real    0m6.164s
user    0m0.000s
sys     0m0.010s

GNU time's elapsed value is off by some factor.

$ \time factor 1111111111111111111
1111111111111111111: 1111111111111111111
0.00user 0.00system 52:39:24elapsed 0%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+0minor)pagefaults 0swaps
$ time factor 1111111111111111111
1111111111111111111: 1111111111111111111

real    0m11.424s
user    0m0.000s
sys     0m0.010s

As above; also here all the running time should be attriuted to user time. This is probably a open issue gnumach.