I'm on probation and today I was arrested for a warrant I had no knowledge of of something I'm accused of that happend a year ago.

The problem with probation violations is that it really depends.  It depends on the nature of the violation, the temperament of the Judge, and your history.  If a Judge finds that you have violated probation then he or she could give you all the time you have over your head.  The Judge could also revoke all, some or none of your time.  They are one of the hardest things to predict.  There are sentencing guidelines, but the judge does not have to follow them.  If you have any new charges then the guidelines don't apply at all.  The best thing to do is to show all of the good things you have done while on probation, how you haven't gotten into any trouble, how you have turned your life around.  It is possible to not be found in violation if the probation officer is wrong or if you do not get convicted of the new charge.  Some times a probation officer will wait to see what happens with the new allegations before saying that you violated.  Though they don't have to.