TAT Offset is a term used in the aviation industry to describe the difference between the actual time of arrival and the estimated time of arrival. It is calculated by subtracting the estimated time of arrival from the actual time of arrival. The acronym TAT stands for 'Time At Target' and the offset is the difference between the two times. This term is important in the aviation industry as it helps to ensure that flights arrive on time and that passengers are not inconvenienced.