Japan put the revised Civil Code into effect Monday, making a change to its presumption of legitimacy system that determines paternity based on when pregnancy and birth occurred.

Under the revised Civil Code, children born after remarriage of their mothers are presumed to be offspring of their current husbands. Previously, such children were presumed to be offspring of the mothers' former husbands if they were born within 300 days of divorce.

This new rule applies to children born on and after Monday, the start of fiscal 2024.