The invention relates to a method and a device for calculating a time window for a time constraint of arrival of an aircraft at a given point, the aircraft receiving wind predictions and including a sensor for measuring the wind. The method includes a calculation of a first time window, and the calculation of an overall confidence index having the determination of a first confidence index on the basis of a deviation between wind predictions and wind measurements performed by the aircraft, the calculation of a margin for the time constraint on the basis of the overall confidence index, and the calculation of a second window on the basis of the first time window and of the calculated margin.