Realtime Clock Synchronization

To ensure time-dependent applications run successfully, the system clock synchronizes with a reliable, Internet-based time source when the system is booted.

Note: You must have a working Internet connection for the system clock to be properly set.

Applications such as The Weather Network and Pandora use SSL to securely access websites they need for their operations. When the system clock deviates from the actual (correct) time, those applications can fail because they can't validate a website's certificate. Changing the time "on-the-fly" can cause key platform components, notably the JavaScript core, to fail. As a result, this operation isn't allowed once the HMI has loaded, so the system clock must be set during startup, before the HMI loads.

On systems without battery-powered backup for their realtime clock (RTC)—such as the Freescale i.MX6Q SABRE Lite board—the clock setting is lost when the hardware is powered off. To address this problem, the system startup script sets the system clock to the RTC's setting. If the date and time are earlier than a threshold time value that's hardcoded for the QNX CAR system, the system assumes the RTC isn't set properly and then tries to synchronize both the RTC and the system clock with an NTP server (which requires an Internet connection).

On hardware that does have battery backup, the RTC is typically set even before the OS image is installed. In this case, the date and time will be later than the threshold time value, so the startup script won't try to synchronize the RTC and system clock.

For more information about the QNX realtime clock, see rtc in the QNX Software Development Platform Utilities Reference.