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The NIST supplies a number of services which form, in effect, a series of tiers of accuracy and levels of automation for the purposes of computer timekeeping. |
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2.7.3.1
Voice Time Service |
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At the first level, NIST operates a voice time service, which is accessible at |
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(303) 499-7111 |
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This number permits 24-hour access and supplies a time mark on the minute. This service can be used to obtain the correct time, for the purposes of a manual update to a system date and time. |
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At the second level of service, NIST transmits time marks on the shortwave radio band, from station WWV located in Fort Collins, Colorado. Transmissions are found at 2.5, 5.0, 10.0, and 20.0MHz. A wide variety of radio clock devices are able to set the time from these transmissions. In addition, a number of projects have been published in computer magazines over the years which describe hardware and related software for accessing these signals and converting them into timing signals for the PC and other computers. The disadvantage to this approach is the investment in additional hardware. |
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The NIST therefore also provides a software approach to setting the time. This is an online time service called Automated Computer Time Service (ACTS). This service is accessible by modem at 300 and 1200bps at |
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(303) 494-4774. |
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ACTS returns a series of strings of ASCII characters with the following format: |
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JJJJJ YY-MM-DD HH:MM:SS dd L s.u mmm.m UTC(NIST) x |
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To put some flesh on these bones, an example string might look like: |
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49999 95-10-08 23:59:35 20 0 +.3 045.0 UTC(NIST) * |
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The format identifiers have the following meanings. |
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JJJJJ The last five digits of the Julian Day number of the date. The date 8 October 1995 is Julian Day number 2449999. |
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