Don't buy this clock to use in an office building. The "atomic clock" features don't work in mine. It wouldn't set itself correctly when I bought it, so I had to set it manually. Yesterday was the fall time change, and it didn't reset itself. Once it's set manually it keeps good time, but the way it's made makes setting it a bit difficult. The fine print on the directions says it won't work in a mall, and I guess that also applies to my two-story office building. I suspect it proabably also applies to appartment buildings.