If you were given a date to turn yourself in and you missed, you violated a court order. It could lead to additional charges or additional time being tacked on to your sentence. Contact your attorney ASAP and get into court. The longer you wait, the worse it will be.
If you have a really good excuse, many judges will just let you start serving the sentence without violating your probation and giving you more time. VERIFIED, DOCUMENTED medical emergency is always a great excuse, but don't think a note from your mother will do it. But take the initiative and calendar the case in court and take your best try at convincing the judge you had a good reason to miss it.
