How to convert in both directions between year,month,day and dates in R?

Question

How to convert between year,month,day and dates in R?

I know one can do this via strings, but I would prefer to avoid converting to strings, partly because maybe the

Answer 1

Found one solution for going from date to year,month,day.

Let's say we have a date object, that we'll create here using ISOdate:

somedate <- ISOdate(2004,12,21)

Then, we can get the numerical components of this as follows:

unclass(as.POSIXlt(somedate))

Gives:

$sec
[1] 0

$min
[1] 0

$hour
[1] 12

$mday
[1] 21

$mon
[1] 11

$year
[1] 104

Then one can get what one wants for example:

unclass(as.POSIXlt(somedate))$mon

Note that $year is [actual year] - 1900, month is 0-based, mday is 1-based (as per the POSIX standard)