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51 |
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NIST time setting format The NIST transmits in its own standard Automated Computer Timer Service (ACTS). It is contacted via TCP/IP on port 13. After a setting is made, the time string from the NIST used in the setting is displayed in the NIST log window. ClockWatch translates this string. All times from NIST are in UTC. This time string is made up of a series of fields arranged end to end. Message Format received from NIST, with an actual sample string below it: MJD YYMMDD HHMMSS DST LS H ADV MISC 49010 93-01-23 22:01:22 00 0 0 50.0 UTC(NIST) * MJD The first number is the date expressed as a Modified Julian Day number (MJD), in the above example 49010 is the Modified Julian Day. The Modified Julian Day: is obtained by counting days from the starting point at midnight on 17 November 1858. It is one way of telling what day it is with the least possible ambiguity. YYMMDD HHMMSS The next 6 value pairs give the Universal Coordinated date and time (formerly called Greenwich Mean Time) as year, month, day, hour, minute and second. DST The eighth number is the daylight saving time flag, DST. It is based on the continental US system, which has transitions on the first Sunday in April and the last Sunday in October. DST = 0 means standard time is currently in effect. DST = 50 means daylight saving time is currently in effect. DST = 51 means the transition from standard time to daylight time is at 2am local time today. DST = 1 means the transition from daylight time to standard time is at 2am local time today. DST > 51 gives advance notice of the number of days to the transition to daylight time. The DST parameter is decremented at 0000 every day during this advance notice period, and the transition will occur when the parameter reaches 51 as discussed above. 1 < DST < 50 gives advance notice of the number of days to the transition to standard time. The DST parameter is decremented at 0000 every day during this advance notice period, and the transition will occur when the parameter reaches 1 as discussed above. The DST parameter is usually |