Finally v17 PDF-Manuals

[Jörg Knebel via 4D_Tech]

Thank you 4D
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RE: How to get the current time in a specified time zone

[Timothy Penner via 4D_Tech]

There are a lot of nuances for timezone data; here are a few that I find 
interesting -

* Is "12:00:00 AM Tuesday" at the beginning of Tuesday or at the end of 
Tuesday? Depends on which year you are talking about and what country you are 
in.

* If you have a timestamp that originates in Russia between 1st and 13th of 
February 1918, is it a valid timestamp? This is the period of time Russia 
switched from Julian to Gregorian calendar thus skipping those days.

* Samoa changed their timezone offset by 25 hours in 2011 so, technically 
speaking, December 30th 2011 never happened in Samoa; a similar (yet opposite) 
occurrence happened in Samoa on July 4th 1892, where July 4th 1892 happened 
twice in Samoa.

The following article is both interesting and funny in how it explains some of 
these nuances:
https://zachholman.com/talk/utc-is-enough-for-everyone-right

-Tim



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Re: How to get the current time in a specified time zone

[Bob Miller via 4D_Tech]

Ah, this is such a complex issue.  You need to know:

- the time zone where your server is (which is where you will get the date 
and time using Current Time(*)
- the time zone where your user is
- the time zone where you want to know what time it is
- whether it is daylight savings time where your server is
- whether it is daylight savings time where your user is
- whether it is daylight savings time where you want to know what time it 
is

This is compounded by the fact that it could be a different DAY in some of 
these zones, as they can be on different sides of midnight.

Fortunately, the computer operating system does a lot of this for you.  I 
use Windows and some time ago asked the excellent people at Orchard 
Software to add sys_GetTimeZoneList to Win32API.  This allows returns an 
array of all time zones with the current GMT offset, taking into account 
daylight savings time, etc.

You might be able to get a similar thing from the Mac operating system.

What I do is capture the user's current time zone from the OS when he logs 
in.  I do this on the server and save it in a table, which I then read 
into a variable on the user's session, so I can calculate the time 
difference between the user and the server.  Then if I need to know the 
time in another area, I have an array of time zones from the OS I present 
to the user and can calculate the time accordingly.

Once upon a time I used a web service to do this, but when I found it was 
all built into the OS, I used that with good results.

Hope this helps -


Bob Miller
Chomerics, a division of Parker Hannifin Corporation


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Use HID Omnikey 3121 USB reader in 4D

[Piotr Chabot Stadhouders via 4D_Tech]

Hi All,

I recently saw a discussion about using USB barcode scanners in 4D

Maybe this is an obvious question, but does anybody know what is the best way 
to interface with an USB (smart card) reader in 4D?
We are going to use the HID Omnikey 3121

Thanks in advance,
Piotr

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