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We use in to describe the physical location of something as part of a larger thing or place. We use at when we're talking about an address, a public place or building (a bus stop, the Post Office, the library etc.) and cases in which the location is irrelevant but what we do there is what matters (school, the dentist, dance class etc.)
When speaking of a period of time in the future, use in, and not after. Here in means after the end of.