What does the keypoololdest field mean? After reading this question I watched the keypoololdest. 


It was 1392447127 (Sat, 15 Feb 2014 06:52:07 GMT)
I created a new address.
Then, it was 1392449568 (Sat, 15 Feb 2014 07:32:48 GMT)


Should the time change to be today at the moment of change? It is too old (like one year ago) . If I took a backup now is it sufficient until the "keypoololdest" changes to be more recent than the date of the backup?
The value 1392447127 is exactly Sat, 15 Feb 2014 06:52:07 GMT in  Unix timestamp 
check it here : http://www.onlineconversion.com/unix_time.htm

keypoololdest gives the unix timestamp of the oldest key in the key pool (which stores unused keys). This timestamp can be used to check if a wallet backup still covers all your used keys or a new one needs to be created.

At the latest, if the timestamp retrieved with keypoololdest gives a date younger than your youngest backup, you should create a new backup.