I whole-heartedly agree that we need to make a system independent of any
sort of time measurement system. I think the conclusion reached on IRC
was that most of the world uses or is at least familiar with the
Gregorian system.
Now, I can't help but think how we would define an Instant. The best
(reasonable) choice is something like TAI or Unix Epoch (I could argue
that seconds are not independent, but don't trust me; I'd suggest
tapping into the cosmic timeline :) ). I also hope there aren't going to
be any leap Instants. (the filter should take care of leaping, after all
the calendar has an issue with leaping.)
If there isn't a standard defining how many seconds are in a year (i.e.
as defined by TAI or the metric system or some other international
standard), I propose it'd be about 365.25 Gregorian days (although I'd
much prefer an international standard to my Indo-European ways :) ).
Overall, I think you have a great idea. As long as the filters are
implemented simply, I think it will prove to be the best option.
--
Don't Panic!
