It is meant to be in total age, that is from hatching to dispatching, but is very rarely an accurate time frame as suggested on the packets. Usually anything from 2-6 weeks longer than claimed is not uncommon. This is due to the fact there are so many variables involved with growing, from type of lights, nutrition, substrate, growing techniques and even temps can all affect how fast or slow a cannabis plant will grow. The times on the packet are derived from optimum EVERYTHING, normally using mega wattage HID lights and hydro, which is a far cry from a dude growing in his basement with a 100 watt blurple light and cheap garden soil.
In my experience, 12 weeks is more like an expected and realistic/average life span.
Hope this helps,........
Organoman.