data.frame

Because it's horribly inefficient. It's using 49 bytes to encode 8 bytes worth of data. If your data set is a few hundred observations this likely doesn't matter. But most users of timeseries data have millions or billions. (I come from a computational finance background.) Even if they were wedded to JSON for some reason, they could have just used a list of observations, like: [1458000000,63.422235], That would have cut their data costs in half. Or just use one of the many existing formats for transmitting time series data. It's not a new topic. https://github.com/mobileink/data.frame/wiki/What-is-a-Data-...