I have a Raspberry Pi that has no access to internet. It is configured as an access point that I can connect to using my smartphone or tablet. Time on the Raspberry Pi is never correct after booting and I want it to automatically sync with the first device that connect to it. Those android devices (smartphone or tablet) will also have no internet access but their time will be correct. Is that possible?
I use the Raspberry Pi to control my telescope mount in a remote area hence the absence of internet. The tablet is just used as a VNC client displaying the Raspi's desktop.
man dhcpcd-run-hooks). Beyond that, network programming for something like this is pretty simple on the Pi, but more complicated on Android.