Can inmates be released during the day and return to sleep or come back for the weekend? My wife is an inmate and I believe she is doing that, but hasn't informed me

Yes, it is possible that a sentence may be served on the weekend only, not normally the other way around. This is in cases where the offense is not considered a threat to the community and the offender is placed in some sort of work release. Weekend furloughs are not the norm, though. If your wife is not coming home when you think she is supposed to, you have a whole other problem to worry about.