Traditional temporal epistemic logic is defective to express perfect recall. It cannot express the memories of individuals’ knowledge. Time and knowledge are integrated into a single operator in the new system S5tCt, such that individual knowledge, general knowledge and common knowledge can be indicated by certain time. With this simple setting, each agent (individual or group) can recall all of their historical knowledge and has memories. The main result of the study is completeness, and it can be proved by using canonical model that S5tCt is complete with respect to the class of all equivalence and monotone decreasing frames.