Time Zone Dialog Help

In this dialog, you must give for each slide of time, the correction to apply to get the UT time.

Each record is made of 2 date/hour, the beginning date/hour and the end date/hour, and the correction to apply between begin and end date/hour to get UT date/hour.

Dialog must be read line by line.

Year:

The year of the beginning (left) or end date (right). You must start far enough in the past, for example -5000.

Day:

The day of the beginning (left) or end date (right). From 1 to 31.

Month:

The month of the beginning (left) or end date (right). From 1 to 12.

Hour:

The hour of the beginning (left) or end slide of time (right). For example 0h2'0".

Correction:

Correction, in hours, to apply to get the UT date. To say that time is local time, put the special value 7777h0'0".

Comments:

Comment for this slide of time.

Note:

With the birth date/time, Proastro will browse the Zx.pra file, x being the number of the Time Zone in the Lonlat file for the Birth City.

Particular pitfalls case with time changes:

Suppose that a person is born the day the time is changing, from wintertime (say UT + 1) to summertime (say UT + 2).
Also suppose that the time change is done by electronic mean.
The person is born at 2h15'0" AM, and the time as changed at 2h AM.
You must notice that this birth hour is wrong, because at 2h 0' 1" time was 3h 0' 1".

How will Proastro react to this?

First, you will get a warning because birth time is near a time change.

Second, Proastro will apply for the birth date/hour the correction local time - 2 h = UT time, so UT time will become 0h 15'. This is wrong, expected UT time is 1h15.
In this case, Proastro is not in fault, because input date was wrong.

Now, suppose the person is born at 1h30' and time is changing back from summer time to wintertime at 2AM.

As incredible as it may seem, there are two 1h30' moments!
First 1h30' time happens before the time change (when 2h become 1h).
The second 1h30' is 30' after the time changes from 2h to 1h.

How Proastro react to this?

First, you will get a warning because birth time is near a time change.

Second, Proastro will apply the summer correction and will find that the UT time is 23h30' of the previous day.
This is right only if the 1h30' hour is the first one.
If it is the second one, UT time must by 0h 30' UT.

So if you get a warning because birth date is too near a time zone, you must check carefully the UT time given by Proastro.

You will even have to do some research to find out the UT time at birth (some time changes are not made by electronic means...)

See also:

Create or modify a time zone file