Sony unveiled the Xperia Z3+ (or Z3 Plus, if you prefer) almost two years ago, in May 2015. Last March, it upgraded the device to Android 6.0 Marshmallow, and now, it's getting a getting a taste of an even newer OS update.
However, as with other devices in Sony's range, the company isn't yet upgrading the Xperia Z3+ to the very latest version of the OS. While Google released Android 7.1.1 Nougat last month, Sony is instead rolling out Android 7.0, which is now five months old.
On top of that, Sony isn't even updating the Xperia Z3+ with the newest security patches; it's rolling out the December security updates rather than those for January, which many other manufacturers have already made available to their devices.
Sony began its Nougat update program in November with the Xperia X Performance, and it's since been expanded to include the Xperia X and Xperia X Compact.
You can see the full list of Sony Xperia devices that will receive the Android 7.0 Nougat update here.