Read this: Windows 8 surpassed Windows Vista in market share with a 5.1% usage rate according to numbers posted in July 2013 by Net Applications, with usage on a steady upward trajectory. However, intake of Windows 8 still lags behind that of Windows Vista and Windows 7 at the same point in their release cycles. Windows 8's tablet market share has also been growing steadily, with 7.4% of tablets running Windows in Q1 2013 according to Strategy Analytics, up from nothing just a year before. However, this is still well below Android and iOS, which posted 43.4% and 48.2% market share respectively, although both operating systems have been on the market much longer than Windows 8. Strategy Analytics also noted "a shortage of top tier apps" for Windows tablets despite Microsoft strategy of paying developers to create apps for the operating system (in addition to for Windows Phone).
Now answer this question, if there is an answer (If it cannot be answered, return "unanswerable"): When did Windows 8 surpass Windows Vistas market share?
July 2013