Sorry for getting off-topic .. but...
23:59:60 is the same (if wold exist) like 00:00:00 and this is the New year...
No: 23:59:60 is not the same as 00:00:00
http://hpiers.obspm.fr/eoppc/bul/bulc/bulletinc.dat
So 31.12.2008 will be 86401 seconds long instead of 86400 seconds.
But anyway.. your good old wall-clock (or ntp server ;-) ) doesn't care :)
Regards, Adrian