You really didn't much give any details, but if you're scheduled for serving time on a weekend and you do not appear, it's very bad. Not only will the judge swear out a warrant for your arrest, and you can expecxt to be in jail when apprehended and it won't just be for a weekend. Your sentencing will likely be reevaluated and you'll do "real time". In additoin, your absconding is a crime in itself and may generate additional jail time.
If you haven't done this yet, I seriously advise that you don't miss your scheduled time. If you have some extremely valid reason, contact the court to see if accommodations can be made (these will NOT be done after the fact).
If you've already missed your session, you better have a lawyer involved./