The book that I'm writing resolves around the lives of multiple characters. Therefore I want every character to have their own chapter (I write in third person though). Each chapter will be based on one of the characters and what's happening to them, and then the next chapter will go to the next character and so on. The only thing is, for example, two of my chapters are about different characters, but they are happening at the same time. How do I make sure the reader knows this is the case? Do I directly tell them with times and dates etc.? Or is there a subtler way to do it. Like, during the writing?