That's also not true. Me touching the keys as I type and the key pushing down are two things that are happening at the same time.
Me typing this and you breathing are happening at the same time. There are so many other examples.
here is a better explanation
There is no such thing as simultaneity unless the two things happened at exactly the same time and place.
Per einstein, if two event happened at different location, you can never determine absolutely if they occurred simultaneously. Different observers travelling at different velocities would say they occurred at different times.
You also have the problem that time is apparently infinitely divisible, which means that even if you agreed as to a frame of reference, you would always be able to find a small bit of time difference whether it be .01 seconds, or .000001 seconds, or something even smaller.