[R] difftime

[eric lee]

Hi.  I'm trying to take the difference in days between two times.  Can
you point out what's wrong, or suggest a different function?  When I
try the following code,  The following code works fine:

a <- strptime(1911100807,format="%Y%m%d%H",tz="GMT")
b <- strptime(1911102718,format="%Y%m%d%H",tz="GMT")
x <- difftime(b, a, units="days")
x


But when I change the year, the following code returns 'NA' for the
time between a and b.  Thanks.

a <- strptime(1999100807,format="%Y%m%d%H",tz="GMT")
b <- strptime(1999102718,format="%Y%m%d%H",tz="GMT")
x <- difftime(b, a, units="days")
x