October 18 has been confirmed by Microsoft as the date for releasing Windows 8.1 and New Zealand will be the first market to get the upgrade at a midnight lauch.
The announcement was made by Microsoft overnight on the official Windows blog, on which a spokesperson said 8.1 would be available as a free upgrade for Windows 8 users through the online Windows Store.
ISO disc images won't be "made available broadly for consumers" the spokesperson said, but Windows 8.1 will go on sale in retail stores by October 19. Pricing for Windows 8.1 was not revealed by Microsoft.
The spokesperson declined to say if TechNet and Microsoft Developer Network (MSDN) subscribers would be able to get the release version of Windows 8.1 ahead of the general release date.
Windows 8.1 contains several under-the-bonnet improvements over the original 8 version, and also tweaks to the heavily criticised tile-based Metro user interface.
Microsoft is expected to launch its new enterprise operating systems at the same time, the Windows Server 2012 R2 family, as these use the same kernel as Windows 8.1.