Y'know, I'm surprised that none of those fancy watches that show lunar
phases, and such, display Julian Dates. Or do they? In any event, I
understand that Swatch beats can be set to any timezone, instead of just
"Biel Mean Time" (actually CET) so if you set one to GMAT, the watch
displays the first three digits of a fractional Julian day, or if to UT, it
displays the MJD fraction.
--
John Hynes
----- Original Message -----
From: "James J. Wentworth" <[EMAIL PROTECTED]>
To: "U.S. Metric Association" <[email protected]>
Sent: Monday, January 16, 2006 5:29 AM
Subject: [USMA:35697] Re: Swatch Time? (Re: Re: decimal time)
Interesting...I'll see if I can snag one off eBay. That feature, while no
doubt a marketing gimmick, could nonetheless be useful. -- Jason
----- Original Message -----
From: "John Hynes" <[EMAIL PROTECTED]>
To: "U.S. Metric Association" <[email protected]>
Sent: Monday, January 16, 2006 1:36 AM
Subject: [USMA:35690] Re: Swatch Time? (Re: Re: decimal time)
This is true; all digital Swatch watches are capable of displaying
thousandths of a day, counting from midnight Central European Winter
Time.
However, the French made decimal time the law of the land during the
Revolution, with weeks of 10 days, each of 10 hours, each of 100
minutes, each of 100 seconds. Clocks still exist showing 10 hours, but
it was unpopular and was suspended on the same day in 1795 that the
original metric system was established into law, without any unit for
time. (The original "republican measures" included the metre, litre,
are, stere, gramme and franc.)
Astronomers and others use decimal time of day, that is, using decimal
fractions instead of subunits. For instance, Julian Dates represent
dates and times with both whole and fractional days (JD 2453751.920) and
many computer programs represent dates and times internally in a similar
fashion; Julian years are represented with a decimal fraction of the
year (J2000.0); and Gregorian calendar dates may include a fractional
day of month to represent time of day (2006 January 16.420). A great
many organizations also use decimal hours, that is, hours with tenths
and hundredths instead of minutes and seconds (12.05h).
A lot of computer software, especially on Unix-type computers, represent
time as a continuous count of SI seconds from some epoch, usually from
1970. Current time of day is determined by dividing this count by 86400;
the remainder is the number of seconds since midnight UTC, which can
then be converted into hours and minutes for humans. A separate count
is usually kept of milliseconds or microseconds or even nanoseconds. A
typical Unix time would be 1137406866 seconds.
The base unit of time interval in the SI metric system today is the
atomic second. Time of day is represented by clocks, and is not the
same as time interval, which is represented by stopwatches. Most civil
time today is based upon the SI second, but this has not always been
true, and does not have to be, although there are advantages in doing
so. Reform of civil time, i.e. time of day, would not necessarily
require any change of metric time interval.
--
John Hynes
----- Original Message -----
From: James J. Wentworth
To: U.S. Metric Association
Sent: Sun, 15 Jan 2006 16:45:27 -0800
Subject: USMA:35682] Swatch Time? (Re: Re: decimal time)
Wasn't the watch company Swatch promoting something somewhat similar
called "Swatch Time" that they measured in "beats" (1000 beats in a day,
I believe)? -- Jason
