Since Tcl 8.5 has unlimited range
integers, I'm mildly surprised by:
% clock format 0x10000000000000000
expected integer but got "0x10000000000000000"
% clock format 0xffffffffffffffff
Wed Dec 31 18:59:59 EST 1969
clock.n is long, and I can't claim
to have read every word, but a quick
scan didn't appear to document a
limited range on valid time values.