What the second Saturn return actually is
Saturn takes roughly twenty-nine and a half years to travel once around the zodiac. That is the whole mechanism. When it arrives back at the exact degree it occupied at your birth, you are having a Saturn return, and because the orbit is what it is, that happens at about twenty-nine, again at about fifty-eight, and for many women a third time in their late eighties.
The first return gets all the attention. It has a whole genre of essays behind it, mostly written by women in their twenties about their twenties. The second gets almost nothing, which is odd, because it lands at the point in a woman's life when the structures she built are either holding or quietly failing, and when the culture has started to look past her. Saturn does not look past her. It shows up on schedule with the same question it asked at twenty-nine, only now she has thirty years of evidence to answer it with.
The dates are not vague. Saturn will cross your natal degree on specific days, often three times across a window of eight to fifteen months because it turns retrograde and passes back over the same point before moving on. The calculator on this site gives you those dates from your birth date alone, with no email and no account.