In most states you would do your time every weekend. The policies of the sheriff's department vary from state to state so the place to start is with them. They let you know if you can be accommodated.
Typically, North Carolina judges will order weekend jail time to be served at the discretion of a defendant’s probation officer. This allows for flexibility and enables your probation officer to work around your schedule. So, you can skip weekends or several weeks, if necessary. In my experience, it is rare for a cour to set a specific schedule at the time of sentencing. Probationers report to their local county jail on Friday afternoon and they are released on Sunday afternoon.
The posting by attorney Patrick Roberts is correct. The judges in North Carolina will rarely set the exact dates for your weekends to be served unless the date has some significance to the offense committed or to the punishment they wish to have you serve (e.g., they have you in jail on the weekend of your birthday for added significance, or over the New Years holiday if you have a drinking/partying-related offense). As long as you have verifiable reasons for skipping a weekend (such as business trip, etc.), the probation officers will usually work with you. Your weekend in jail in Wake County (Raleigh, NC, the capital) run from 6:00 p.m on Friday night through 6:00 p.m. on Sunday night. Come with some reading materials and expect to sleep on a mat on the floor due to crowding in the Wake County Jail.