Date Values
Dates are represented as the number of days since 1970-01-01, with negative values for earlier dates.
# use as.Date( ) to convert strings to dates
mydates <- as.Date(c("2007-06-22", "2004-02-13"))
# number of days between 6/22/07 and 2/13/04
days <- mydates[1] - mydates[2]
Sys.Date( ) returns today's date.
date() returns the current date and time.
The following symbols can be used with the format( ) function to print dates.
| Symbol | Meaning | Example |
| %d | day as a number (0-31) | 01-31 |
| %a %A |
abbreviated weekday unabbreviated weekday |
Mon Monday |
| %m | month (00-12) | 00-12 |
| %b %B |
abbreviated month unabbreviated month |
Jan January |
| %y %Y |
2-digit year 4-digit year |
07 2007 |
Here is an example.
# print today's date
today <-
Sys.Date()
format(today, format="%B %d %Y")
"June 20 2007"
Date Conversion
Character to Date
You can use the as.Date( ) function to convert character data to dates. The format is as.Date(x, "format"), where x is the character data and format gives the appropriate format.
# convert date info in format 'mm/dd/yyyy'
strDates <- c("01/05/1965", "08/16/1975")
dates <- as.Date(strDates, "%m/%d/%Y")
The default format is yyyy-mm-dd
mydates <- as.Date(c("2007-06-22", "2004-02-13"))
Date to Character
You can convert dates to character data using the as.Character( ) function.
# convert dates to character data
strDates <- as.character(dates)
Learning More
See help(as.Date) and help(strftime) for details on converting character data to dates. See help(ISOdatetime) for more information about formatting date/times.
To Practice
This intermediate R course includes a section on working with times and dates.