In the R language, the classes "POSIXct" and "POSIXlt" are representing calendar dates and times (to the nearest second).
The classes POSIXct and POSIXlt are representing calendar dates and times in R.
The class POSIXct represents the (signed) number of seconds since the beginning of 1970 (in the UTC timezone) as a numeric vector.
Class POSIXlt is a named list of vectors representing
- sec: seconds (0-61)
- min: minutes (0-59)
- hour: hours (0-23)
- mday: day of the month (1-31)
- mon: months after the first of the year (0-11)
- year: years since 1900
- wday: day of the week, starting on Sunday (0-6)
- yday: day of the year (0-365)
- isdst: Daylight Savings Time flag. Positive if in force, zero if not, negative if unknown.
POSIXct is more convenient for including in data frames, and POSIXlt is closer to human-readable forms. A virtual class POSIXt exists from which both of the classes inherit.
References:
- Ripley, B. D. and Hornik, K. (2001) Date-time classes. R News, 1/2, 8–11.
