Nina18 is between Nina17 and Nina19
It was just called to my attention that the nina18.cha file has a typo in the date given at the top. Specifically, it claims that nina18.cha was from 1970, but it must be from 1971, given that the age attributed to Nina increases by 4 days (not -361 days) between nina17.cha (in 1971) and nina18.cha. …