This article discusses general time-domain modeling in electromagnetics, considering why time-domain modeling may be worth doing and some choices to be made among the principle modeling approaches, and briefly traces the evolution of present time-domain modeling. The steps involved in developing and using a time-domain model are discussed as are some specific aspects of performing time-domain modeling using differential-equation- and integral-equation-based models. An in-depth discussion of more general issues that can arise in time-domain modeling is presented. Finally, time-domain applications are characterized with respect to computer requirements. A representative list of some available time-domain software is also presented along with some concluding comments.