On Sat, 21 Jun 2008, Chad Giffin wrote: > > We currently (normally) store time as the number of elapsed seconds > since January 1st 1970 GMT. NTP represents time as an unsigned 32 bit integral number of seconds since 1900-01-01 00:00:00 plus 32 bits of fraction, i.e. the whole timestamp is 64 bit fixed point. This wraps a couple of years before 32 bit Unix time_t. The TICTOC working group was recently chartered to specify highly accurate time and frequency distribution. See http://www.ietf.org/html.charters/tictoc-charter.html It's not possible to specify a timestamp format that both fits in 64 bits and has sufficient range and precision to be useful for most purposes. FreeBSD's bintime format uses standard time_t (eventually 64 bits) plus 64 bits of fractional seconds, i.e. the whole timestamp is 128 bit fixed point. The high precision avoids aliasing problems when representing multi-GHz clock frequencies (e.g. CPU clocks). Tony. -- f.anthony.n.finch <dot@xxxxxxxx> http://dotat.at/ HEBRIDES BAILEY: NORTH 5 TO 7, BUT GALE 8 AT FIRST IN HEBRIDES, BACKING WEST 3 OR 4 LATER. ROUGH OR VERY ROUGH, DECREASING MODERATE LATER. SHOWERS. GOOD. _______________________________________________ IETF mailing list IETF@xxxxxxxx https://www.ietf.org/mailman/listinfo/ietf