The Galaxy S6 was released on the 1 April 2015^[1], which marks the beginning of its update period. On the 6 August 2018, the Android 9 was released, a next version of the operating system, which not made available for the Galaxy S6, thus leaving Galaxy S6 on the the previous version of the operating system, the Android 8. This date marks the end of what we consider its update lifetime.

These two dates are 3 full years and 4 full months apart, which gives it C tier.