Dear Heinz, Thanks, let me see.
* Heinz Tuechler <tuech...@gmx.at> [2023-01-31 01:02]: > Dear Jean Louis, > > it appears to me that you mix two aspects. I agree with you that a time > zone needs an offset from UTC to be defined. Consequently the definition > of a time zone requires an offset. Yes, that is good our mutual understanding. > But an offset does not need a time zone to define a time. I am trying to understand what you wanted to say with the above. Before representing time with the UTC offset: --------------------------------------------- To derive the representation of time with the UTC offset, one needs time zone, as UTC offset is defined in the time zone. That is what you also said above. After representing time with the UTC offset: -------------------------------------------- That time is defined, and at that time point does not need time zone. I am not concerned of time representation after UTC offset has been derived, but of programming calculations to users' local time, as for example in Org Agenda. > For example, true mean local solar time of a specific longitude can > be described by UTC plus offset. Solar time - Wikipedia: https://en.wikipedia.org/wiki/Solar_time By meaning that solar time should be related to longitude, I am totally with you Heinz. It is also true that one could disregard the definition of UTC offset from the political reality, and calculate it absolutely. That condition I have already mentioned, when I said, that means we are making "new type of time" in Org, if we start calculating it that way. The meaning of "UTC offset" is however, political. Please see the UTC offsets here: https://upload.wikimedia.org/wikipedia/commons/8/88/World_Time_Zones_Map.png Look at the map, find Kazakhstan with UTC offset +6 on the same longitude with Russian Federation with UTC offset +5. Observe Kazakhstan with UTC offset +6 on the same longitude with China with the UTC offset +8. That alone should tell you that solar time is not really related to UTC offset, but we could say it is "approximate" with few hours more or less. Of course you can describe solar time with UTC offset, but do not assume it will be accurate. > I agree with your criticism of "They refer to local *solar time* at a > particular place." This is written in > https://en.wikipedia.org/wiki/UTC_offset , but not even there the > description is consistent. We can say it is approximate what they mean. > Of course, for every finite offset, we can find a corresponding > particular place (a longitude). I wish it would be so, but it is not so. It is approximate, just look at the map. And please tell me if after this you still think there is something wrong? -- Jean Take action in Free Software Foundation campaigns: https://www.fsf.org/campaigns In support of Richard M. Stallman https://stallmansupport.org/
