Can someone please tell me the usage of 'in which' and 'when' when we are talking about a timeframe mentioned in the first part of the sentence,
My instinct about this says that to the extent that they're used as relative pronouns, "when" implies more of a single moment, whereas "in which" implies that the timeframe has a duration. Another way to think of it might be that "when" is more of an "at which" in time, while "in which" is more of a "during which" or a "throughout which."
So:
"I will call you when I'm free" means "I will call you the moment at which I cease to be busy."
"The year in which I worked three jobs was crazy" means "I worked three throughout this year (duration), and let me tell you, it was crazy."
