One way to picture latter-day: a long line of time, with your finger resting near the end of it — the days closer to now. Whatever the word touches belongs to that later stretch, not to the beginning. Sometimes it is a period (latter-day students). Sometimes an old famous role is carried forward into that stretch and worn by someone living (a latter-day Edison).
Wiktionary gives the word as latter ('close or closer to the present time') plus day. That is the whole picture: the later part of a stretch of time.
Wiktionary 記錄這個字由 latter（接近或更接近現在的）加上 day 組成。這正好就是整個畫面：一段時間裡比較後面、比較靠近現在的那一部分。
Wiktionary (kaikki extract 3f6f69a190036ae4, entry 'latter-day', source_ref kaikki:3f6f69a190036ae4:1204021305:7625): From latter (“close or closer to the present time”) + day.
From the picture
現代版的某位名人
一樣站在時間線靠後的那一段上，只是這次不只是標時間，而是把一個古早的名字搬過來。先想到過去那個有名的人或地方，再指著現在這個很像的：a latter-day Edison、a latter-day Tsar。時間還是「後面這一段」，被填進去的是一個舊角色。
adjective · C1
Used before the name of a famous person or thing from the past, to describe someone or something that exists now and fills a very similar part.
現代版的…
adjective · C1
Belonging to a recent period of time rather than an earlier one; used in front of a noun.
近期的；後來的
adjective · C2
Relating to the last days of the world as some religions describe them. It is used mainly inside fixed names, above all the Church of Jesus Christ of Latter-day Saints.
末世的；後期的（宗教）