Hello!
Probably less and less people use the Blynk local server, but there are still some situations when “offline” functionality is needed: for example in remote areas without internet connection, or in mobile devices which are “travelling” thorough different countries and permanent internet connection would be a challenging or expensive solution.
We use the local server in our off-grid motorhome in Europe, and I couldn’t rely on internet for the server functionality. So, we have a RPI zero w2 as an access point and server in the same time. One of the issues with this setup is that there is no internet connection to sync the date / time on the server. Recently I realised that in Europe there is the so called DCF77 radio signal (with coverage nearly in all Europe), which can be used to receive date and time with atomic clock precision.
To receive this data, one needs only a low cost receiver and some rpi or arduino coding… This way it is possible to keep the time without internet or physical RTC module 
Maybe it will be helpful for others… I’ve just ordered some modules and will see how it works.