"Date"representing calendar dates.
as.Date(x, ...) "as.Date"(x, format, ...) "as.Date"(x, origin, ...) "as.Date"(x, tz = "UTC", ...)"format"(x, ...)"as.character"(x, ...)
"%Y/%m/%d"on the first non-
NAelement, and give an error if neither works. Otherwise, the processing is via
as.Date(origin, ...)to such an object.
as.charactermethods return a character vector representing the date.
NAdates are returned as
as.Datemethods return an object of class
formatso the answer will be of length that of the longer of the vectors.
Locale-specific conversions to and from character strings are used where appropriate and available. This affects the names of the days and months.
as.Date methods accept character strings, factors, logical
NA and objects of classes
"POSIXct". (The last is converted to days by ignoring
the time after midnight in the representation of the time in specified
time zone, default UTC.) Also objects of class
package date) and
package chron). Character strings are processed
as far as necessary for the format specified: any trailing characters
as.Date will accept numeric data (the number of days since an
epoch), but only if
origin is supplied.
as.character methods ignore any
fractional part of the date.
localesto query or set a locale.
Your system's help pages on
strptime to see
how to specify their formats. Windows users will find no help page
strptime: code based on glibc is used (with
corrections), so all the format specifiers described here are
supported, but with no alternative number representation nor era
available in any locale.
## read in date info in format 'ddmmmyyyy' ## This will give NA(s) in some locales; setting the C locale ## as in the commented lines will overcome this on most systems. ## lct <- Sys.getlocale("LC_TIME"); Sys.setlocale("LC_TIME", "C") x <- c("1jan1960", "2jan1960", "31mar1960", "30jul1960") z <- as.Date(x, "%d%b%Y") ## Sys.setlocale("LC_TIME", lct) z ## read in date/time info in format 'm/d/y' dates <- c("02/27/92", "02/27/92", "01/14/92", "02/28/92", "02/01/92") as.Date(dates, "%m/%d/%y") ## 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 ## incorrectly 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) ## Experiment shows that Matlab's origin is 719529 days before ours, ## (it takes the non-existent 0000-01-01 as day 1) ## so Matlab day 734373 can be imported as as.Date(734373, origin = "1970-01-01") - 719529 # 2010-08-23 ## (value from ## http://www.mathworks.de/de/help/matlab/matlab_prog/represent-date-and-times-in-MATLAB.html) ## Time zone effect z <- ISOdate(2010, 04, 13, c(0,12)) # midnight and midday UTC as.Date(z) # in UTC ## these time zone names are common as.Date(z, tz = "NZ") as.Date(z, tz = "HST") # Hawaii