text: how long can you spend  in jail on a felony 4? i have already been in jail for 3 weeks, and i have been told that they can only keep me for 30 days, then i have been told 18 months. well, you aren't very specific..are you still awaiting trial?  if so, there is no time limit per se.  however, once you are sentenced, there is a limit as to how long a county jail will keep you.  in ca, if you are sentenced to over 1 year for a felony, then you go to prison.  if it's less than 1 year, then you stay in county.  i believe each state has a time limit they can hold you after arrest without filing charges.  so that may be the 30 days they are talking about.   please don't listen to everything prisoners say.  a few really do know the system, but most of them know just a little bit.  afterthought?...you have internet access in jail?  sounds more like camp snoopy