I have a general question about the time library. I understand that there are multiple ways to keep time on an Arduino. I'm really only concerned with two of them, the first being an RTC, and the second an NTP update using the ethernet shield.
So this may seem basic, but I'm really struggling to find an explanation. I understand how an RTC works, how to set it, and how to request the specific register data after the time has been set. Regarding an NTP request, I also understand how the process works, returning a serial number for epoch time.
Where I get confused is - if I do not use an RTC and use only an NTP time request, do I need to request an updated time from the server every time I need to access time? In other words, is there a way for the Arduino's internal clock to keep track of the current time after I make a single NTP request, or do I need to request the time from the NTP server each and every time I want to access the current time? Ideally, I'd like to request an updated time from the NTP server every hour, or maybe even every day. However, I might like to access the current time in between update intervals without hitting the NTP server again.
I appreciate any comments or explanations.