SYSTEM

A system comprising a real time clock, RTC, and a processor configured to execute a secure application to provide a secure clock and configured to operate in a first low-power-mode and a first normal-mode, and a non-secure application configured to perform a clock modification procedure and configured to operate in a second low-power-mode and a second normal-mode, the system configured to perform a secure clock initialisation procedure comprising obtaining a record of a current time from the RTC based on a transition from the first low-power-mode to the first normal-mode, wherein the secure application is configured to perform a clock update procedure including updating the RTC with a secure record of the current time and wherein the system is further configured to prevent performing the clock modification procedure after the clock update procedure has been performed.