Women’s participation in tertiary education has been increasing since the second half of the 20^th century and, in many countries, since the 1990s, tertiary-educated women in their reproductive ages outnumber tertiary-educated men. This structural change had consequences for union formation behavior. The expansion of women’s educational attainment has challenged the persistence of conventional union patterns, in which women tend to mate with men who have higher social status and older age. In this paper, we examine the interaction between changes in educational assortative mating and age-difference between partners over time. We used IPUMS harmonized census microdata of four countries (Brazil, France, Panama, and United States), which have available data since the 1960s. We found that expansion of education is favorable to increasing age homogamy over time, especially for the higher educated. Educational hypergamy and age hypergamy, however, have become less compatible over time. Educationally hypergamous unions have become more heterogeneous in terms of the age-difference between partners, contrary to the overall trends for other couples.