Person time is calculated by summing the amount of time each individual in the study is at risk for the outcome of interest. For example, if a study follows three individuals for 1, 2, and 3 years respectively, the total person time would be 6 person-years. This measure can be applied to various units of time, such as person-days, person-months, or person-years, depending on the study design and the nature of the outcome being measured.
