On Wed, 2 Mar 2011, Luis Felipe Parra wrote:
Hello. I am using some dates I read in excel in R. I know the excel origin
is supposed to be 1900-1-1. But when I used as.Date with origin=1900-1-1 the
dates that R reported me where two days ahead than the ones I read from
Excel. I noticed that when I did in R the following:
as.Date("2011-3-4")-as.Date("1900-1-1")
Time difference of 40604 days
but if I do the same operation in Excel the answer is 40605. Does anybody
know what can be going on?
We cannot know: you say a difference of 2 and report 1!
As the examples from as.Date says
## Excel is said to use 1900-01-01 as day 1 (Windows default) or
## 1904-01-01 as day 0 (Mac default), but this is complicated by Excel
## thinking 1900 was a leap year.
## So for recent dates from Windows Excel
as.Date(35981, origin="1899-12-30") # 1998-07-05
## and Mac Excel
as.Date(34519, origin="1904-01-01") # 1998-07-05
So the origin you used is off by 2 days: one for the origin being day
1 and one for Windows Excel's ignorance of the calendar.
Note too that these are *default*: they can be changed in Excel.
Thank you
Felipe Parra
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