"The release of Windows 10 RTM has been confirmed for July 2015," tweeted WZor, who regularly leaks information about Windows and non-public builds of the operating system.
WZor did not elaborate, but in a subsequent reply to another tweet said, "Microsoft is behind schedule with RTM but the late July sounds reasonable to me."
RTM, for "release to manufacturing," is a Microsoft label for the milestone when code is considered sufficiently stable to pass along to device makers, or OEMs (original equipment manufacturers).
WZor was not the first to call out July as a likely Windows 10 RTM timeline. Last month, the CEO of chip maker Advanced Micro Devices (AMD) said that Windows 10 would launch at the end of July. Her comment was related to AMD's chip inventory and orders from its customers.
Even under that schedule, analysts were skeptical that OEMs would be able to put products on shelves in time to make the back-to-school sales season, one of the two most important selling stretches in the U.S.
Microsoft has declined to confirm the July timetable, and has stuck with its wider "summer" window for the new OS.
Meeting the RTM mark does not necessarily mean that users will have access to Windows 10 at the same time. Historically, Microsoft has reached RTM several weeks before officially releasing an OS to either the general public or its volume license customers.
Three years ago, Microsoft declared RTM for Windows 8 on Aug. 1, 2012; the OS released to the public on Oct. 26, for an interval of just over 13 weeks. In 2009, Windows 7 RTM preceded public release by 14 weeks. (The Windows 8.1 minor upgrade featured a much shorter lag between RTM and launch, just seven weeks.)
If WZor is on the mark, Microsoft will have about the same length of time as Windows 8.1 for Windows 10, since it has committed to releasing the latter "this summer." On the calendar, summer in the northern hemisphere ends Sept. 22.
Windows 10's launch date is of great interest -- more so than for the run-of-the-mill new OS -- because Microsoft will offer consumers and many small businesses a free upgrade from Windows 7 and 8.1 for a one-year post-launch period.