A generation is usually counted as somewhere between 20 and 25 years. As in, enough time for an infant to grow into an adult and then have their own children.

2022-1945 = 77

people give birth around age of 25

    1: the adults in 1945
    2: their babies became parents in 1970
    3: their babies became parents in 1995
    4: the babies of the parents in 1995 are now adults and are giving birth to the next generation

there have been 4 generations since ww2