A trusted time service is provided that can detect resets of a real-time clock and re-initialize the real-time clock with the correct time. The trusted time service provides a secure communication channel from an application requesting a timestamp to the real-time clock, so that malicious code (such as a compromised operating system) cannot intercept a timestamp as it is communicated from the real-time clock to the application. The trusted time service synchronizes wall-clock time with a trusted time server, as well as protects against replay attacks, where a valid data transmission (such as transmission of a valid timestamp) is maliciously or fraudulently repeated or delayed.