(Author's Note: I did do some research throughout the LTT site, and did not see any posts with the actual date. If a post exists, I have missed it in my searching and apologize for the duplicate post.)
Well, I had the Windows 10 upgrade program pop up letting me know that I could reserve my copy of Windows 10 a few weeks ago. At the end though, I saw a date, but neglected to look. After a little digging, I found an FAQ from Microsoft (below) that says what day people can get Windows 10.
Here is an excert from the article:
"Microsoft is making Windows 10 available as free upgrade for qualified Windows 7, Windows 8.1, and Windows Phone 8.1 devices. It will be available starting July 29, 2015; people can reserve their free upgrade today.
You only have until July 29, 2016 to take advantage of this offer. Once you upgrade, you have Windows 10 for free on that device."
Full Article: http://www.microsoft.com/en-us/windows/windows-10-faq?ocid=win10_auxapp_context