Windows 7:
End of mainstream support - January 13, 2015
End of extended support - January 14, 2020
Windows 8:
End of mainstream support - January 9, 2018
End of extended support - January 10, 2023
What is the difference between mainstream support and extended support?
Mainstream support—Microsoft will offer mainstream support for a minimum of 5 years from the date of a product's general availability, or for 2 years after the successor product is released, whichever is longer. For example, if you buy a new version of Windows and five years later another version is released, you will still have two years of support left for the previous version.
Extended support—Microsoft will offer extended support for either a minimum of 5 years from the date of a product's general availability, or for 2 years after the second successor product (two versions later) is released, whichever is longer.