Chapter 7 Time series analysis
POSIX format is a standardised format and by definition an 8 Bit long character value. The POSIX (Portable Operating System Interface) standard has been introduced to guarantee compatibility between different operating systems.
check these functions/types:
ISOdate, ISOdatetime, strftime, strptime, date difftime julian, months, quarters, weekdays
strptime() to cenvert between different character representations of these types.
strftime() (wrapper for format.POSIXlt and format.POSIXct) to extract parts of POSIX times and return them as character strings. Further wrappers for convenience are weekdays() julian(), quarters().