Date and time functions in R

In library(survival), we can find the following functions:

• as.date

  Converts any of the following character forms to a Julian date: 8/31/56, 8-31-1956, 31 8 56, 083156, 31Aug56, or August 31 1956.

  Example:

  > as.date(c("1jan1960", "2jan1960", "31mar1960", "30jul1960"))
  [1] 1Jan60  2Jan60  31Mar60 30Jul60
  

• mdy.date

  Given a month, day, and year, returns the number of days since January 1, 1960.

  Example:

   

  > mdy.date(3, 10, 53)
  [1] 10Mar53
  

• date.mdy

  Convert a vector of Julian dates to a list of vectors with the corresponding values of month, day and year, and optionally weekday.

  Example:

   

  > a1<-mdy.date(month = 8, day = 7, year = 1960)
  > a1
  [1] 7Aug60
  > date.mdy(a1)
  $month
  [1] 8
  
  $day
  [1] 7
  
  $year
  [1] 1960
  
  > 
  

• date.mmddyy

  Given a vector of Julian dates, this returns them in the form ``10/11/89'', ``28/7/54'', etc.

  Example:

   

  > date.mmddyy(mdy.date(3, 10, 53))
  [1] "3/10/53"
  

• date.ddmmmyy

  Given a vector of Julian dates, this returns them in the form ``10Nov89'', ``28Jul54'', etc.

  Example:

   

  > date.ddmmmyy(mdy.date(3, 10, 53))
  [1] "10Mar53"
  

• date.mmddyyyy

  Given a vector of Julian dates, this returns them in the form ``10/11/1989'', ``28/7/1854'', etc.

  Example:

   

  > date.mmddyyyy(mdy.date(3, 10, 53))
  [1] "3/10/1953"