I don't know why, but the display is not actually showing the clock value, however I am able to see the functionality of all the buttons, the slider, and the page concepts. I am guessing it has something to do with the fact I have an Arduino Uno, and am using one of the Basic displays, but I am not positive.
I would not expect that using a basic display would cause a problem, I was careful to design the code to use the minimum of the resources available on a Nextion and everything in this tutorial has been tested on a NX4827T043, which is one of the basic Nextion displays.
A Uno might be a problem as the only serial port is the one used for the USB connection to your PC, so using it for connection to a Nextion (or anything else) means you have 2 different serial connections fighting each other. I did originally test everything using a Uno and I didn't find any problems, however, given that, theoretically at least, there might be problems I have not stated in the introduction that any of this works with a Uno. For changes to this tutorial I mostly test on a Mega, and sometimes on an MKR1010.
One side note: The Nextion website lists print to be depreciated and it looks like it will add a length attribute, but it seems you can limit the number of bytes sent as well.
Thanks, I didn't notice that, I appreciate you pointing it out. I have updated the demonstration files to use prints, which I see replaces print. If you find I've missed any please tell me (I think I only used print for the scroll bar, but there's always the possibility I used it elsewhere and forgot!)
++Karma;