Dear experts, I am doing a simulation of beta decay, and I use the nuclide Bi-214. Then I try to get the time of final tracks, including their global time and local time. The question is that: for beta decay, why the final tracks do not emit at the same time? Also, what is the definition of Local Time in the G4Track class. you in advance. Good luck for you. Best regards, Pigxue Dear Pigxue, GlobalTime is the time since the start of the event. LocalTime is the time since the track was created. It appears that you don't print the times at ever step. You print them only when a track stops. You should find that the GlobalTime is the same - at the start - for all secondaries from beta decay. Gumplinger Peter Dear Peter, Thanks for your reply and helping me solve the problem. Best regards, Pigxue