Convert date objects to ratetable form
This method converts dates from various forms into
the internal form used in
a date. The function currently has methods for Date, date, POSIXt, timeDate, and chron objects.
This function is useful for those who create new ratetables, but is
normally invisible to users.
It is used internally by the
functions to map the various date formats; if a new method is added
then those routines will automatically be adapted to the new date type.
a numeric vector, the number of days since 1/1/1960.