I'm importing xls
files using gdata
. I am converting date columns using as.Date
to convert the date
As per the manual for as.Date
, the date origin is platform dependent, and so I am determining which origin to use accordingly
.origin <- ifelse(Sys.info()[['sysname']] == "Windows", "1899-12-30", "1904-01-01")
as.Date(myData$Date, origin=.origin)
However, I'm wondering if I should be considering the platform where the file is being read or the platform where it was written?
For what it's worth, I am currently testing the code on a linux box with no excel, and the correct Dates are produced by using origin="1904-01-01"
Quoting `?as.Date'
## date given as number of days since 1900-01-01 (a date in 1989)
as.Date(32768, origin = "1900-01-01")
## 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
## treating 1900 as a leap year.
## So for dates (post-1901) 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
## (these values come from http://support.microsoft.com/kb/214330)
You could try out the (extremely) new exell package: https://github.com/hadley/exell. It loads excel dates into POSIXct, correctly choosing the origin based on whether the file was written by Windows or Mac Excel.