It is not unusual for a person sentenced to 364 days in county jail to be eligible for release in just over 4 months. "Eligible" means just that. There is no guarantee that an inmate will be released on his earliest eligibility. The most important considerations would be his prior record and the nature of the offense. A person serving time for a "violent" crime is less likely to get early release than a non-violent offender.
You can check the code but I believe you must serve 60 days before they begin calculating good time and work credits. You normally can reduce the remaining sentence substantially. It also depends on how crowded the jail may be and other factors. So 4 month is possible in Hudson County but I think they may do a tad more.