Re: Calculating days and dates (was: Re: 360 degree/Fabian)

2011-01-25 Thread Richard B. Langley
Calendar math is an exercise in modulo arithmetic. See for a peek into the topic. -- Richard Langley Quoting Tony Finch : On Tue, 25 Jan 2011, John Pickard wrote: If you need to check days of weeks for arcane date

Re: Calculating days and dates (was: Re: 360 degree/Fabian)

2011-01-25 Thread Tony Finch
On Tue, 25 Jan 2011, John Pickard wrote: > > If you need to check days of weeks for arcane dates, JoneSoft Date Calculator > is a free program that will give you the day of the week for just about any > date, and the number of days between two specific dates. You only need about two lines of code

Calculating days and dates (was: Re: 360 degree/Fabian)

2011-01-24 Thread John Pickard
Good afternoon all, Frank King noted that A good many people don't know the day's date without checking but most know the day of the week. It would be odd to have the date changing at one time and the day at another. If you need to check days of weeks for arcane dates, JoneSoft Date Calcul

Re: 360 degree/Fabian

2011-01-20 Thread Tony Finch
On Thu, 20 Jan 2011, Brad Lufkin wrote: > I think having the JDN change at noon UTC avoids a lot of confusion. > Consider this: when is Thursday midnight? Is it the instant between > Wednesday and Thursday or the instant between Thursday and Friday? With the > current definition, it's crystal clea

Re: 360 degree/Fabian

2011-01-20 Thread Brad Lufkin
On Thu, Jan 20, 2011 at 12:29 PM, Brad Lufkin wrote: > I think having the JDN change at noon UTC avoids a lot of confusion. > Consider this: when is Thursday midnight? Is it the instant between > Wednesday and Thursday or the instant between Thursday and Friday? With the > current definition, it's

Re: 360 degree/Fabian

2011-01-20 Thread Brent
Napoleons' last orders to his troops at Waterloo: Napoleon: Alright men, listen up, we will attack precisely at 8 o'clock today. Private #1: You mean we will attack tonight in the dark? Napoleon: No, 8 o'clock tonight is actually tomorrow. Private #2: But it is already past 8 o'clock today.

Re: 360 degree/Fabian

2011-01-20 Thread Mike Shaw
<> I guess that, if you are an astronomer, you don't want the date changing half way through your viewing session. Mike Shaw 53.37N 3.02W www.wiz.to/sundials PS By the way, we seem to have gone away from our previous convention of adding our latitude and longitude in our signatures. It i

Re: 360 degree/Fabian

2011-01-20 Thread Frank King
Dear Andrew (and Fer), Many thanks for this reference... http://www.aandc.org/research/nautical_time_and_date.html That is a splendid article and shows just what pitfalls one can fall into when attempting to force historical data to fit the present way of thinking! I share your thought...

Re: 360 degree/Fabian

2011-01-19 Thread fer de vries
al Message - From: "Frank King" To: Cc: "Sundial List" Sent: Wednesday, January 19, 2011 5:44 PM Subject: Re: 360 degree/Fabian Dear Brent, You correctly note... It looks like the date must have changed at noon. Indeed so. Interestingly, even with GMT (as used by a

Re: 360 degree/Fabian

2011-01-19 Thread Frank King
Dear Brent, You correctly note... > It looks like the date must have changed at noon. Indeed so. Interestingly, even with GMT (as used by astronomers and navigators) the date used to change at noon (which was referred to as 0h GMT). This was the case until 1 January 1925, so not very long ago!

Re: 360 degree/Fabian

2011-01-19 Thread Brent
Fabio; That's a great sundial. It looks like the date must have changed at noon. That makes perfect sense as the beginning and end of each day would be simple to witness, impossible to do at midnight. However, that would be a difficult leap for societies who do most of their activities from