methods and apparatus , including computer program products , for radio frequency identification label time synchronization . a method includes , in a radio frequency identification interrogator having an antenna , transceiver , a clock , a memory and a central processing unit , initializing a rfid tag with a label start time and a time to record data , the label start time representing an actual start time indicated by the clock , receiving a label stop time , a label time and logged data from an interrogation of the rfid tag , and compensating the label time for a drift between the label stop time and an actual stop time .