[Optional] using so many functions in your Javascripts codes breaks the rule of OOD (object oriented design) pattern of the application, you could put all of those functions into your class, making them methods, and calling every method that needs to be initialized from a class constructor

while creating html elements dynamically with javascript it would be better using innerHTML than creating each element and adding it to the previous one using appendChild(), because subsequent call to dom elements is less optimized.

Having your time update on page refresh doesn't utilize the flexibility of live update functionality JavaScript gives you. You could use a JS setinterval functionality to update time every second. note: which could be less optimized but its a small price to pay for dynamicity