Suhur/sahri is the pre-dawn meal eaten before a fast. The end time of suhur is when Fajr begins. We MUST use the Fajr time of the CORRECT day to stop eating suhur and start praying Fajr. e.g. today is Tuesday and Zayd is fasting. He will break his fast at the time of Maghrib/sunset that his timetable lists for Tuesday. Zayd eats iftar and some time later, he prays Isha according to the time listed for Isha for Tuesday. Thus, the Tuesday salahs are now finished. Zayd then intends to fast on Wednesday. So he will use the time listed for suhur ending for WEDNESDAY, not Tuesday. It is seen that some people are using the time of Tuesday for the fast of Wednesday, etc. The confusion may be because in their mind, it is still Tuesday night at the time of suhur so they abide by the Tuesday timing. Whereas at the time of the said suhur, we are at the time of Fajr on Wednesday. Please check your individual timetables and ensure you are reading them correctly.