Guys, DUT1 is the UTC correction in units of .1 second determined by the International Earth Rotation Service (IERTS) and disseminated to the public by radio, satellite and telephone. It decrements every few months or so. When DUT1 hunts the outskirts of -5 it increments one second and a leap second is declared in UTC.
While tweaking the audio reference clocks I discovered a mystery. The CHU broadcast signals show +0 for the DUT1 correction, as does the NIST modem time. However, the WWV signal last I checked showed +1. Intrigued, I checked the NIST web http://tf.nist.gov/timefreq/pubs/bulletin/leapsecond.htm and found it said the correction has been +1 since 28 September 2006. A polite note from the CHU operators said the +0 is correct, but they received notice only hours before it went into effect. Well, according to IERTS Bulletin D http://hpiers.obspm.fr/eop-pc/ dated 15 December 2006, the DUT1 was changed to +0 on 22 December, just in time for Christmas. Then, I checked WWV again and found DUT1 +0. Apparently, I must have last checked before 22 December. Life moves fast. Curious, I looked for evidence why the IERTS declared when it did. Looking at the daily data, the predicted DUT1 crossed .05 s on the way down on 23 December midway between 0.1 and 0.0, so the criteria must be round to the nearest decisecond. The scary part is the increased rate DUT1 is dropping. Dave _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions
