We dinged Sony for shipping the Xperia Z with an old version of Android, but the company is catching up today by posting an upgrade to Android 4.2.2. Most owners receiving the update are carrying unbranded HSPA+ and LTE models at this stage, although there are reports of at least a few carrier-specific phone variants getting the refresh. As with the Xperia ZL update, most of the user-facing changes are minor. The biggest addition is support for lock screen widgets; there's also slight (if noticeable) tweaks to the interface look and feel. If those revisions are still meaningful enough for you, we'd suggest a quick upgrade check through the usual desktop and OTA channels.
Source:Sony Mobile forums