You get half time credit up front and it depends on what you pled to, etc, but no more than 90 days and likely much less. If you had an attorney, they'd be the best person to ask.
A great deal will depend on which county jail you are speaking about. In many jails it will be half time. In over crowded jails it will be less. Your attorney will have a better idea of what is going on in your county. Good luck.
for Fairness / for Your Freedom because sometimes good people get into bad situations
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I'd love to be able to give you an answer, such as 2.2 months or something quite specific. However, as most lawyers will say, it matters. It matters what type of offense you are being sentenced for - is it a DUI? It is a violent offense? It also matters on how full the jail is right now. I have recently had clients serve a full 30 days on a 30 day jail sentence and others serve less than a day on a 60 day sentence. It matters on the type of offense, how old you are, which jail you go to, how large it is and sometimes, if the jail employees like you. Do you have any medical issues that require special attention?
Penal Code section 4019 is the code section concerning custody credits. It was amended by Assembly Bill (AB) 109 in part recently to help "realign" California's prison population by sending more folks to county jails that would previously have been sent to prison. County jails then became more crowded and often released folks to probation. AB109 is really just one of five legislative enactments over the last two years or so (Senate Bill 18, Senate Bill 76, Assembly Bill 109, Assembly Bill 117 and Assembly Bill 17) that may affect the length of your jail time.
Without knowing more about the conviction, I simply cannot tell you much.