Windows 10 receives the first notable upgrade from its public launch, a cumulative update that comes with the KB3081424 code and we receive from Windows Update. Gabriel Aul himself announced this new update, although not saying that news brings.
As you mentioned in the comments some have already started to notice small changes to the calendar, but of little importance. At the moment we have no list of new or improvements brings so we rely on what we see with the naked eye. Have you seen any news or change in your Windows 10 ?
To update, go to Settings > Update & Security > Windows Update and download KB3081424 update.