Daylight Savings Time Function

[JSpicolli]

Anyone got a function that will return a bool, depending on if Eastern time is currently on Daylight Savings time?

I need to convert EST to GMT, but the offset differs by an hour depending on if we are on Daylight Savings Time or not.

GMT_OFFSET = 5
IncidentTime = dateAdd("h", GMT_OFFSET, TIME)


Muchos Gracias

 

[JSpicolli]

Determining DST is a real #$@!

http://webexhibits.org/daylightsaving/b.html

Anyone run into a similar requirement?

Any tips are appreciatted.

 

[ethorn10]

haven't tried this but just thinking while typing...

could you write something to scrape

http://www.greenwichmeantime.com

(look for this text 'Clocks in Europe / USA / Canada on Summer / Daylight Saving Time until 30th October 2005' -- or even just part of it) and then apply your offset?

like i said...haven't written/tested anything...just a thought.

 

[JSpicolli]

In case anyone else ever needs this functionality:

<% 
    ' fill in your known bias here! 
 
    offset = 5 
 
    ' find first Sunday in April 
 
    for i = 1 to 7 
        if weekday("4/" & i & "/2001")=1 then 
            startDST = cdate("4/" & i & "/2001") 
            exit for 
        end if 
    next 
 
    ' find last Sunday in October 
 
    for i = 31 to 25 step -1 
        if weekday("10/" & i & "/2001")=1 then 
            endDST = cdate("10/" & i & "/2001") 
            exit for 
        end if 
    next 
 
    ' set some arbitrary date 
 
    od = "06/28/2001 4:35:08 AM" 
 
    ' subtract hour from offset if within DST 
 
    if cdate(od) >= startDST and cdate(od) < endDST then 
        offset = offset - 1 
    end if 
 
    nd = dateadd("h", offset, od) 
     
    Response.Write("Current = " & od & "<Br>UTC = " & nd) 
%>

http://www.aspfaq.com/show.asp?id=2218

 

[vongrunt]

I haven't checked yet, but looks like startDST and endDST must be greater for 2 hours (change occurs at 02:00AM).

------
"There's a man... He's bald and wears a short-sleeved shirt, and somehow he's very important to me. I think his name is Homer."
(Jack O'Neill, Stargate)

 

[johnwm]

Nice function - unfortunately only works in a few parts of the world. Not even the whole US agrees on DST settings. A page related to your previous (

http://webexhibits.org/daylightsaving/g.html)

gives some clues, but misses out large chunks of the world. A (slightly) more comprehensive list:

http://www.worldtimezone.com/daylight.htm

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