Patent ID: 7411868

Claim:
A method performable by an untrusted time device comprising: upon communicatively connecting to a trusted time device, (a) acquiring a trusted current time from the trusted time device; (b) storing an elapsed time, elapsed from the trusted current time; (c) determining an estimated current time based on the trusted current time and the elapsed time; (d) storing a time difference between the estimated current time and an untrusted current time of the untrusted time device; (e) repeating (b)-(d) until the untrusted time device has been turned off; upon the untrusted time device being turned on again, where the untrusted time device is able to communicatively connect to the trusted time device, (f) repeating (a)-(e); where the untrusted time device is unable to communicatively connect to the trusted time device, (g) determining a temporary current time based on the time difference last stored in (d) and the untrusted current time of the untrusted time device; (h) comparing the estimated current time last determined in (c) with the temporary current time; (i) where the estimated current time last determined in (c) is less than the temporary current time, setting an offline current time equal to the temporary current time; and, (j) where the estimated current time last determined in (c) is greater than the temporary current time, setting the offline current time equal to the estimated current time last determined in (c).