The time he served, plus any additional conduct credits, will be deducted from the two years he was ordered to serve. He will then serve half of what's left.
Example: He served four months before sentencing. He will get another four months of credit for good behavior. (That's true for most inmates; sex offenders, people convicted of violent felonies, and those with a prior "strike' offense would get less.) That's 24 months in prison, minus 8, which gives him sixteen months left.
The Department of Corrections usually applies half time from the date of sentencing. That means he will serve half of the sixteen remaining months, which works out to about eight months.
He will get an "out date" when he is processed through the reception center -- a prison where new inmates are evaluated and sent to the facility where they will serve their time.
He should have received the time in County jail doubled for good time work time. Once he is out of jail, he will be sent to be classified by the Department of Corrections (this usually takes about 90 days). Once he is classified, then he will be eligible to received good time work time. From what I have been hearing, after classification, inmates are only serving 35% of their remaining time. You my want to confirm this with the Dept. of Corrections. The most he would do is half of his remaining time, once classified...assuming he did not plead to a strike.
He'll get credit for all time spent in county jail (pre-sentencing credits). Plus he gets an additional 50% (unless its for certain serious/violent felonies). So, assume 180 days actual time in county jail - add 90, for a total of 270 days. He'll do 1/2 time of the 2 year sentence (or 1 year) LESS time already served (270 days per my hypothetical). The Department of Corrections will give your friend what is called an "S.E." date (sentence end). Good Luck & God Bless.
Judith M. Fouladi
Partner, Criminal Defense Advocacy
Bohm, Matsen, Kegel & Aguilera, LLP
DISCLAIMER: This answer is provided as general information, which may not be appropriate for the specific facts of your particular situation. No attorney-client relationship has been established based on this limited communication. You are advised to consult with an attorney in your jurisdiction before taking any action or inaction that may affect your legal rights.