Android : get time from server to close to do trial

I want to make checking about the current time of the server and check if my application passed that day , then the application should stop working

I made a research but I wasnt able to make it working as many examples I think they missing some thing

for example this post

Creating an Android trial application that expires after a fixed time period

I see it uses extends BaseMainActivity where is the "BaseMainActivity" so I can extend it !!

and how the checking for the date and time get should be done

and should I use alarm manager to check that server for the time ? or there is another better solutions