Date-time must be a POSIXct, POSIXlt, Date, chron, yearmon, yearqtr, zoo, zooreg, timeDate, xts, its, ti, jul, timeSeries, and fts objects.
a date-time object
an object for which the
the date of x as a Date
date() can be called without any arguments to return a string representing
the current date-time. This provides compatiblity with