Systems and methods for providing trusted time service for the off-line mode of operation of a processing system. An example processing system comprises: a first processing device communicatively coupled to a real-time clock, the first processing device to modify an epoch value associated with the real-time clock responsive to detecting a reset of the real-time clock; and a second processing device to execute, in a first trusted execution environment, a first application to receive, from the first processing device, a first time value outputted by the real-time clock and a first epoch value associated with the real-time clock.