Time is ubiquitous, fundamental, and relevant to nearly all adaptive behavior. Over the last century or more, key fundamentals of time perception and timing behavior have been discovered and described. Theoretical and neurobiological models have been developed to help explain, describe, and predict behavior under the control of time. In this chapter, some of the fundamentals of timing behavior and its quantitative modeling will be reviewed. There will be a focus on common behavioral procedural arrangements, their relevant dependent measure outcomes as they pertain, particularly, to timing accuracy and precision, and the mathematical modeling of those outcomes using commonly employed strategies. The timing literature is robust and continues to hold promise for better understanding behavior, particularly as it relates to adaptive behavior in health and disease/disorder in humans.