[R] RODBC & POSIX & Daylight Saving blues
murdoch at stats.uwo.ca
Fri Nov 12 17:55:21 CET 2004
On Fri, 12 Nov 2004 16:27:41 +0000, Bernie McConnell
<bm8 at st-andrews.ac.uk> wrote :
>Many thanks for the responses about how to read datetimes into POSIXct
>which refer to straight GMT times without regard to Daylight Saving. To
>reiterate, I''m using R 2.0.0 on win2000.
>I have tried Gabor's suggestion,see below, which did not work for me. The
>fundamental setting (for me) appears to be in the registry:
>The values here are most readily altered using the 'Date/ TIme properties'
>window (just double click the wee digital clock on the right of the window
>task bar). When I disable Daylight Saving a registry variable
>called DisableAutoDaylightTimeSet is created and is set to 1. This can be
>observed with regedit. Now all works perfectly with my date handling. So
>it seems that setting the timezone to GMT is necessary but not sufficient
>for my needs
>I confess that I do not understand the relationship between setting
>registry variables and environment (eg TZ="GMT").
>In practice I would like to keep my win200 machine with Daylight Saving
>enabled - for the sake of other applications. One strategy is to make the
>required registry alterations immediately before and after any R code which
>handles dates. But then I'm rather worried whether continuously enabling /
>disabling Daylight Saving would have dire consequences for other
>applications and the well-being of my already shaky OS. Is this the right
>route - and if so could someone please guide me how to achieve this in R
>Perhaps a better strategy would be to introduce some set-able option within
>R that forced date handling to ignore Daylight Saving. But here I have
>insufficient expertise and can only appeal to the continuing generosity of
>the developer community.
>I am sure that there are many R users in the same position as me - but
>perhaps they don't all realize it!
I think you probably want to use as.is=TRUE when you retrieve the
results, then use the date conversion functions to specify the time
zone explicitly, e.g. asPOSIXct(x, tz='GMT').
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