> There is no provision in the NIST WWV/H/B timecode for a leap deletion
This is not true. Let me explain in detail below. > nor is ther provision in the hardware timecode generators for that. The This is true. > DUT1 is a signed adjustment to the current UTC to produce UTC1. The Yes, and it's this same DUT1 sign bit that tells you if the leap second is to be inserted or deleted. Think about it... As DUT1 gradually goes from positive to negative in 0.1 second increments over the months, IERS announces a leap second, and the WWV* leap second pending bit is lit. User software reading the WWV* subcode can tell if the leap second is positive by the fact that the DUT1 sign is negative. By contrast if the Earth were to speed up for a while DUT1 will be gradually increasing, and as it climbs in 0.1 second increments into positive territory and approaches +0.9 s, IERS will be forced to declare a negative leap second, and WWV* will set the leap second pending bit. User software reading the WWV* subcode can tell if the leap second is negative by the fact that the DUT1 sign is positive. So it may be tricky, and not obvious on first reading, but the WWV* timecode format, as defined by NIST, is capable of handling negative leap seconds should they ever occur. You and I both know privately that the old transistor TCG in Ft Collins can't handle dropping a second at this time, but that's hardware. The point I'm trying to make is that the timecode format can handle both types of leap seconds. Provision for negative leap seconds is implicit in any timecode that contains both a boolean leap second pending bit and a DUT1 sign bit. > adjustment changes sign after a leap second to reflect the current > offset of UTC1 from UTC. The DUT1 sign has nothing to do with the > insertion/deletion of the leap. Think about it - the only reason we need leap seconds is that DUT1 is non-zero and has a sign. ;-) Perhaps code speaks clearer than words. Take a look at the WWVB TCG source code at: http://www.leapsecond.com/notes/wwvb1.htm and http://www.leapsecond.com/notes/wwvb2.htm Example of leap years, positive, and negative leap seconds are posted there. /tvb _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions
