You'll have to store more information, you just need to decide what is more space efficient. A possible approach would be to store both the bucket total, as wel

You'll have to store more information, you just need to decide what is more space efficient. A possible approach would be to store both the bucket total, as well as the components to an equation that can roughly model the rate of change within the histogram. If you find an equation that generally models observed rates dependent on time `t`, then you can interpolate an approximate value for any point in time. You can get sliding windows out of this as well, by using the equations for adjacent periods. You'll incur a runtime cost for this of course, but relatively small.