generating Unique id with date and time in id

Hi,
I have to generate unique ids to insert in oracle database as primary key for a table with time and date in the id. Many users can insert at the same time in the table.
i will purge the database records 2 months old so thinking if there are any potential problems in using auto increment kind of logic.

Will sequence in Oracle can be of any help?

Any suggestions are welcome.

Thanks in advance...
[ June 27, 2007: Message edited by: Karan Jain ]

My advise: don't put logic in auto-generated id's.
If you need a unique id, then let Oracle's sequence mechanism generate one for you.
If you need to purge data older than two months, then create a field in your table to store the creation date.
It's better not to mix things up.
And you have a chance to write a performing purge query if the creation timestamp is in an Oracle date field, not if the date is hidden somewhere in a part of your unique id.

Regards, Jan

Thanks a lot Jan,
I agree to your suggestion and using the same...