Time Dataset was Last Changed
DESCRIPTION:
Returns the time at which a permanently stored version of a dataset (object) was last modified.
USAGE: 
dataset.date(name, where=1, date.format=10)
REQUIRED ARGUMENTS:
name:
character string naming a dataset stored on database where.
OPTIONAL ARGUMENTS:
where:
a number identifying a database in the search list.
date.format:
integer specifying in which format the dataset date should be returned. Currently recognized values are 1 for an integer like 717805635, measuring seconds since 1 January 1970 00:00 GMT; 10 for a string like "Tue Sep 29 15:27:15 1992"; and 11 for "92.09.29 15:27".
VALUE:
if where refers to a directory database, the time of the last modification to the permanently stored version of this dataset. Note that datasets are not permanently stored until the end of a top level expression unless you use synchronize() or assign(..., immediate=T) to force early storage.

The return value "NA" (or -1 for integer format) means that the dataset does not exist on the database. "0" (or 0 for integer format) is returned for the special dataset .Random.seed, whether it exists or not. Zero is also returned for any object in a non-directory database.

SEE ALSO:
assign , objects.summary , synchronize .
EXAMPLES: 
  x <- 10
  dataset.date("x")
[1] "Tue Sep 29 16:55:09 1992"
  d <- dataset.date("x", date.format=1)    # as number
  x <- 20
  dataset.date("x", date.format=1) - d
[1] 5    # The assignments to x were 5 seconds apart.