There are many theories about what time is. What is the future, and what is the past? Do they exist at all? Is there only one future and one past? Is the universe really fundamentally indeterministic, or is everything predetermined? I can't answer these questions, and maybe humanity will never be able to do so, but we can think about the implications different natures of time would have.
I like determinism. I like the idea that everything follows a fixed set of rules, that with infinite computing power and memory, it could be perfectly simulated. But with quantum mechanics, many started to believe the universe to be truly random at it's core. The many-worlds interpretation of quantum mechanics offers a possible solution, a compromise between both possibilities. Instead of thinking about the things that happen as truly random and how probable they are, it assumes every possibility is real, and that some things being more probable than others is the result of there being more such similar worlds. It sounds nice, the universe stays deterministic, but we can't predict the future, even though it's just because there is no single future. But I think from a philosophical standpoint, this is the worst possibility.
Imagine having a very large quadratic piece of paper. Now, cut it into 2^16 quadratic pieces. Enumerate the pieces starting at 0, and draw a grid of 8x8 on each piece. If you look at the number of each piece in binary, you can assign a digit to each cell of of it. Now, fill out only the cells you've assigned a 1 to. You've now a piece for each possible combination of a 8x8 grid with some cells filled out. Also, we can calculate the index of the piece from the pattern on the grid and vice versa. We now put the pieces ordered on a single stack.
Now, take a new piece of paper and draw an 8x8 grid on it. Then draw anything on it by filling out some squares. We could now take the same piece from our stack of paper pieces by just calculating the index. We can also do the opposite, we can take a piece from the stack and draw it. Or we could simulate drawing the squares by calculating the index of the corresponding piece on our stack and then taking the correct piece from the stack.
Our stack every possible piece has become like our fresh white paper. There is no difference between taking a piece and drawing on some squares on a new fresh one. But doesn't that mean like there is no drawing on the new fresh piece, there is no drawing as long as you don't take any from the stack? Doesn't that mean, if only the stack exists, just like if only a blank piece of paper exists, there is no drawing?
Sure this was just an 8x8 grid, but this should work similar for any system where all possibilities already exist. If we apply this to the many-worlds interpretation of quantum mechanics, it would mean that because everything happens, nothing happens. If everything already exists, nothing really exists.