Oh, dear. I have made a mistake. I had not realized that I was dealing with purists who love to argue.
Here are my understandings of the time scales: UTC: Civil time, what most people mean by time of day. Was determined by star crossings at Greenwich, now related to TAI in that both use the same oscillator frequency. Leap second: An adjustment made to UTC to keep it civil. The Earth slows down at an unpredictable rate. In the current history of UTC, the Earth has never speeded up or needed a change other than at July or September. UT1: Astronomers time, also related to TAI by frequency but adjusted more closely by star crossings. TAI: Atomic time, maintained by counting atomic oscillations averaged over many atomic clocks. Monotonically increasing. UT was born in 1928. There are several numbered versions. My little program served the needs of civil time. It backs up at 59 seconds because the display software can't handle 60. That seems close enough for civil work. If you must have monotonically increasing time then it is a mistake to use civil time. You want TAI because you are not concerned with time of day. In fact, civil time is corrected by seconds because civilians don't measure time closer than a human reaction time. As to not handling the leap second interval as 59, 60, 0, what do you do when the Earth speeds up and it goes 59, 1? If the variations are due to the mantle floating on the core, there probably will come a time when it speeds up. As to manually setting a leap second switch with only 6 month's notice, I don't understand your problem. I'd rather have a one month notice so it didn't get postponed until the notice was forgotten. I believe Mills' NTP has a leap second flag that automates that part of the process. Could it be that most computers don't have leap second code because they get their time with NTP? It's pretty civil. I'll grant you that you can write thousands of lines of code to get a GUI to do something right. My field is industrial process control. It is important that timestamps on alarms and events be monotonically increasing. Before MS took over the computing systems, I worked with one that had a rate adjustment, like a mechanical clock. Range was +/- 128 seconds per year. You had to report to the Plant Manager to be authorized to set anything but the rate. Most users didn't use savings time because a one hour overlap is too confusing when your alarm list is sorted by timestamp. Regards, Bill Hawkins ...as we approach 100 messages on this subject since 4 July. _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
