Hello all,

Could someone help me with the time zones in understandable & practical way?
I got completely stucked with this.

Have googled for a while and read the manuals, but without solutions...



-------------------------------------------------------------------

When data imported  from Excel 2007 into R (2.13)

all time variables, depending on date (summer or winter) get (un-asked for
it!) a time zone addition CEST (for summer dates) or CET (for winter dates).



> Dataset
        Start                  End1              End2
days2End1.from.Excel    days2End2.from.Excel
days2End1.in.R               days2End2.in.R
1  2010-01-01      2011-01-01      2012-01-01
365                                     730
365 days                      730.0000 days
2  2010-02-01      2011-02-01      2012-01-01
365                                     699
365 days                      699.0000 days
3  2010-03-01      2011-03-01      2012-01-01
365                                     671
365 days                      671.0000 days
4  2010-04-01      2011-04-01      2012-01-01
365                                     640
365 days                      640.0417 days
5  2010-05-01      2011-05-01      2012-01-01
365                                     610
365 days                      610.0417 days
6  2010-06-01      2011-06-01      2012-01-01
365                                     579
365 days                      579.0417 days
7  2010-07-01      2011-07-01      2012-01-01
365                                     549
365 days                      549.0417 days
8  2010-08-01      2011-08-01      2012-01-01
365                                     518
365 days                      518.0417 days
9  2010-09-01      2011-09-01      2012-01-01
365                                     487
365 days                      487.0417 days
10 2010-10-01     2011-10-01      2012-01-01
365                                     457
365 days                      457.0417 days
11 2010-11-01     2011-11-01      2012-01-01
365                                     426
365 days                      426.0000 days
12 2010-12-01     2011-12-01      2012-01-01
365                                     396
365 days                      396.0000 days

> Dataset$Start
 [1] "2010-01-01 CET"  "2010-02-01 CET"  "2010-03-01 CET"  "2010-04-01 CEST"
"2010-05-01 CEST" "2010-06-01 CEST" "2010-07-01 CEST" "2010-08-01 CEST"
"2010-09-01 CEST" "2010-10-01 CEST" "2010-11-01 CET"  "2010-12-01 CET"

> Dataset$End1
 [1] "2011-01-01 CET"  "2011-02-01 CET"  "2011-03-01 CET"  "2011-04-01 CEST"
"2011-05-01 CEST" "2011-06-01 CEST" "2011-07-01 CEST" "2011-08-01 CEST"
"2011-09-01 CEST" "2011-10-01 CEST" "2011-11-01 CET"  "2011-12-01 CET"

> Dataset$End2
 [1] "2012-01-01 CET" "2012-01-01 CET" "2012-01-01 CET" "2012-01-01 CET"
"2012-01-01 CET" "2012-01-01 CET" "2012-01-01 CET" "2012-01-01 CET"
"2012-01-01 CET" "2012-01-01 CET" "2012-01-01 CET" "2012-01-01 CET"



Variables 'days2End1.from.Excel  and 'days2End2.from.Excel'   are calculated
in Excel.



Same calculation (with same outcome!) I would like to be able to perform
with R.



Variables 'days2End1.in.R' and 'days2End2.in.R are calculated with R.



> Dataset$days2End1.from.Excel
 [1] 365 365 365 365 365 365 365 365 365 365 365 365



> Dataset$days2End1.in.R <- with(Dataset, End1- Start)

> Dataset$days2End1.in.R


Time differences in days
 [1] 365 365 365 365 365 365 365 365 365 365 365 365
attr(,"tzone")
[1] ""


> Dataset$days2End2.from.Excel
 [1] 730 699 671 640 610 579 549 518 487 457 426 396



> Dataset$days2End2.in.R <- with(Dataset, End2- Start)



> Dataset$days2End2.in.R
Time differences in days
 [1] 730.0000 699.0000 671.0000 640.0417 610.0417 579.0417 549.0417 518.0417
487.0417 457.0417 426.0000 396.0000
attr(,"tzone")
[1] ""



Quastion 1:



As you can see 'Dataset$days2End2.in.R' gives wrong 'day' calculation at
time period April until October, when CEST (summer) times are recorded

 640.0417 610.0417 579.0417 549.0417 518.0417 487.0417 457.0417

giving decimals on days, where round days expected (640 610 579 549 518 487
457).





Can someone explain me how to deal with it in R?

What is the best way to calculate days in R getting correct calculations?



Question 2:



As I only need to work with dates without time and without time zones, I
would be happy  to remove them if possible.

I tried already the trunc() function but without succes. The result doesn't
change.



> Dataset$days2End2.in.R.TRUNC <- with(Dataset, trunc(End2)- trunc(Start))

> Dataset$days2End2.in.R.TRUNC
Time differences in days
 [1] 730.0000 699.0000 671.0000 640.0417 610.0417 579.0417 549.0417 518.0417
487.0417 457.0417 426.0000 396.0000
attr(,"tzone")
[1] ""




I would be happy if someone could light up this thing.



Many thanks in advance!

Laura

	[[alternative HTML version deleted]]

