The free upgrade to Windows 10 ended on July 29th, however, as expected, not everyone had taken the chance to upgrade. Luckily for them, it appears they may not need to shell out $119/$199 to upgrade to Windows 10. According to YouTuber vwestlife, simply changing your system's clock to July 28th will re-activate the Upgrade Prompt and allow the upgrade to be started.
Once the clock has been changed to July 28th, the prompt will provide the option to start the upgrade. After clicking that, it will begin downloading Windows 10 and the installation will commence.
For those wondering if this actually works - it does, according to a Redditor, who was previously suspicious of whether this trick would work or not. Entering a Windows 7 key into Windows 10 also still works.
It is not clear how long this trick will work for; it is possible that Microsoft has a grace period, in which it will still accept activations for those people where downloading took a little longer to complete, however, if you missed the deadline to upgrade for free and still wish to do so - give this a try!
One other method of obtaining the upgrade for free is Microsoft's offer that assistive technology users will continue to be able to upgrade for free - check out our post on how that works here.