If you want to extract the year, month, ... from the data POSIXlt class may be more convenient. Use as.POSIXlt() to convert to this class then use varName$year+1900, varName$month, varName$mday, varName$hour, varName$min and varName$sec to extract the year, month, day of month, hour, minute and second of the data/time. (Here varName is the name of the POSIXlt variable).
There is a mistake in my last post: to extract month one should use varName$mon+1 instead of varName$mon. Sorry for that. See the R help DateTimeClasses {base}:
Details
There are two basic classes of date/times. 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
0–61: seconds
min
0–59: minutes
hour
0–23: hours
mday
1–31: day of the month
mon
0–11: months after the first of the year.
year
years since 1900.
wday
0–6 day of the week, starting on Sunday.
yday
0–365: day of the year.
isdst
Daylight Savings Time flag. Positive if in force, zero if not, negative if unknown.
Not quite sure what you meant in the last post. The function as.POSIXlt() will convert the string into a list which represents date and time. Here is my test (R-2.12.2):
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