The phrase "to happen at the same time" means that two or more events occur simultaneously or simultaneously, or that something occurs simultaneously with something else. Full definition
This change in food abundance happened at the same time as the fall in adult cod populations. (sciencemag.org)
But there is a phrase «correlation does not prove causation», which is to say, just because things happen at the same time doesn't mean one thing caused the other. (northcountryvet.com)
However, it is a fact that this cycle does not happen at the same times in all breeds of cats. (tinpaw.com)