A variance is permission to depart from a dimensional rule of the zoning code, such as a setback, a height limit or a minimum lot size, because of something unusual about the property. In most of the United States it is decided at a public hearing by a board of zoning appeals, also called a board of adjustment or, in some states, a zoning hearing board.
Most of the time goes to the calendar. The application has to be complete, then the hearing has to be advertised: a newspaper notice, letters to nearby owners and often a sign on the property, each with a minimum number of days set by state law or the local code. Boards usually meet once or twice a month and have filing deadlines weeks before each meeting. Put together, a straightforward request commonly takes several weeks to a few months from filing to decision, and a deferral adds a month or more each time.
The board weighs a legal test, not a preference. Most states ask whether strict application of the rule would cause an unnecessary hardship because of conditions peculiar to the property, whether the hardship was created by the owner, and whether the variance would harm neighbors or the public. Many states do not allow a variance to permit a use the district forbids; that takes a rezoning instead.
After the vote there is usually a written decision and a short window in which the applicant or a neighbor can appeal to court, so work that depends on the variance often waits for that window to close. In South Carolina, for example, as in Charleston, variances go to the board of zoning appeals under the state's planning enabling act.