babies born on October 10; New Year's Day conception
Refers to the folk belief that babies born on October 10 were conceived on New Year's Day, based on the typical 10-month (lunar) gestation period. The date 10/10 is read as とつきとおか, literally 'ten months and ten days'.
Babies born on October 10 are sometimes said to have been conceived on New Year's Day.
normal gestation period; nine months
Used to refer to the typical human gestation period of about nine months, expressed as 'ten months and ten days' in the traditional Japanese lunar calendar count.
十月十日 is a term that expresses the standard human gestation period.