The most recent 3 generations of Pixels have 7 years of support from launch. One of the hardware requirements for GrapheneOS is 5-7 years of firmware and driver security patches. We continued allowing 5 years to avoid locking ourselves into Pixels since it's the hardest requirement from https://grapheneos.org/faq#future-devices for major OEMs to fulfill. Most of the rest are done for them by Qualcomm with a flagship Snapdragon SoC.
The numbers on that site aren't quite right. For the Pixel 8a, May 14th, 2031 is 2036 days from now which is ~5.58 years rather than 5 years. They're using the 1st of the month instead of the launch day and for some reason the number of months is also sometimes dropped. In practice, a Pixel being launched in May will mean it's going to get a final update in May and the first missed update will be June rather than May. That means their end dates are 1 month early in practice. Not clear why the number of months gets dropped for some of the values they show such as the Pixel 8a.
