"Outlook.com uses Exchange ActiveSync to sync your mail, calendar, and address book on your smartphone, tablet, in the new Outlook 2013 and with the Mail, Calendar and People apps on your new PC or tablet running Windows 8. You can also use the Outlook connector to integrate your calendar with previous versions of the Outlook desktop software. Connecting your calendar to your mobile device is easy."
Microsoft officials hinted last summer than the calendar refresh was coming shortly after the new Outlook.com Web mail service was announced, which was July 31, 2012. But up until today, officials have declined to say when users could expect the updated Calendar.
Update: One feature some were expecting, but that seemingly didn't make it into this calendar update is Skype integration. Supposedly that is still coming, but it's yet another one of those things for which we don't have an official date target.