UT time from ADB

[tetra...@gmail.com]

Good morning,

I was looking into the ADB birthdates, and I lack some knowledge on how were the birth dates defined - and how UT can be calculated.

I assume that when the dates are given in local mean time, given for instance stmerid="m4e54", we must add 4+54/60 degrees to the longitude of the place (assuming east positive).

But let's supose the following record:

ctimetype="s" stimetype="standard time" stmerid="h4w"

Do we subtract here 4 hours to the time, that is, 60º?

And the records where the stmerid="h0w"? Does these means that they are not in summer time or have a different timezone?

Is there some documented formula for these calculations?

Sorry for the inconvinience.

Cheers,

Charles

[Alois Treindl]

When on talks about clock times, one must be aware of the timezone on
refers to.

If you say someone is born at 6:00 am, this does not allow yet
calculation of the horoscope.

You need to know the timezone.

'Standard meridian' is a way an astronomer will express time zone.

Each notation of time refers to a standard meridian.

For example, I am in Switzerland. We use in winter the standard meridian
for Central European time, which is 15° East. In summer, we use the
standard meridian for Central European summer time, which is 30° east.

I can express the standard meridian in degrees, or in hours. 15 degrees
make 1 hour.

In Astrodienst data (and in ADB export data), we prefix the standard
meridian value with 'm' if it given in degrees, and with 'h' if it is
given in hours.

For Swiss winter time, we can write 'h1e' or 'm15e', both mean the same
thing.

For Swiss summer time, we can write 'h2e' or 'm30e', both mean the same
thing.

If you have the clock time, and want to know universal time, you need to
add or subtract the standard meridian.

Again for Switzerland in the winter, at standard meridian 'h1e': we are
east of Greenwich.

UT = given_time - standard meridian for east,
UT = given_time + standard meridian for west.

Swiss time 6:00 am in winter: UT is 5:00
Swiss time 6:00 am in summer: UT is 4:00


h0w is the same as h0e, it means standard meridian 0°, or time is
already in UT.

For dates before the introduction of zone times, we usually have local
mean time. The standard meridian is the longitude itself.

[Alois Treindl]

When standard meridian is h4w it means the timezone is 4hours west of Greenwich. It is obvious that UT is already 4 hours later.

UT = given time + 4 hours





(sent from iPhone)

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[Alois Treindl]

I have added a short explanation to the online documentation:
Computing Universal Time UT
http://www.astro.com/astro-databank/Help:XML_export_format#Computing_Universal_Time_UT

On 14.07.16 11:51, tetra...@gmail.com wrote:

[tetra...@gmail.com]

Good evening Alois,

Thank you very much for the clear and simple explanation :)

Cheers,

Charles