cut out specified time content of system.log

Hi, I'd like to to know is that possible some commands can be cut out specified time content of system.log?

For example,

A) Today is 2014-10-02 and now I want to cut out the shutdown time after 10:30 PM on 2014-10-01. If found out the shutdown time than 10:30, system will collect and zip the user account information and data (include warning log, user operation log, etc) and then mail to specify email address.

B) Is that possible to extend preservation system.log file time? I want the log can be save 12 months.