Hi, me and a friend were discussing calendars and how they go wrong. Apparently one orbit around the sun happens during, on average, 365.242189 rotations around earths axis. The persian calendar almost nails it, with a 1 sec per year error, because it is based on star observations rather than trying to fit rotations to orbits. But we started thinking could we slow down the earth rotation by adding more mass to the moon? Would it be theoretically possible to collect asteroids to the moon to the extent that earth would slow down to 365 days per year. Well that was before I learned that the earth rotation is already slowing down and will eventually be much slower. So instead. Is it theoretically possible to engineer earths rotation to keep a perfect 365 day per year, for our convenience? Or, maybe some other frequency like 100 days per year, as I understand, weather would get nicer, i.e. less wind, which could off course be detrimental to earth cycles in the biosphere though?