This behavior usually occurs when the device does not have access to the Internet: at boot, Android tries to connect to google.com to verify the connectivity. If this step fails, Android does not connect to the NTP server and retrieve the time & date, and it reverts back to the factory timestamp.
To fix this, make sure that the device is connected to the Internet. If the device always displays "No Wifi", refer this article for possible solutions: The Wifi is disabled (no network) when I boot the device
Note
If you are using Genymotion Desktop with QEMU (Linux, macOS), this may occur when using quick boot. Try a coold boot instead. See Genymotion Desktop on-line documentation.