Thanks to the Yin and Yang calculations brought from China, Shinto has adopted a system of yakudoshi, or inauspicious years. In the past, mysterious calculations were necessary, but now the priests have decided that all women have their most inauspicious year when they are 33 years of age, and men when they are 42. People of these ages visit their shrine for a ceremony or at least buy a protective amulet (omamori).
Below is a photo of a sign in the Fujinomori Shrine asking attention for the bad years. These are counted as kazuedoshi, that is in the old system where you were already one year old at birth (meaning you have to add one year to all these figures - 33 is in fact 34, and 42 is 43, etc.). As people are not used to this system anymore, the years of birth are written behind them.
The inauspicious years are in red; also the year before and after that age is "bad." In addition, for men 25 and 61 are weak years, and for women 19 and 37.
It is all totally unscientific, and I don't know how many people still fall for it. Sometimes Japanese just like to take part for the fun of it without asking themselves such difficult questions. My Japanese family strongly disliked it. But when a religious institution finds a way of making money from the gullible, it will cling to it for ever!