There are conflicting sources for when the character named 'Tanya Hernandez' was renamed 'Tasha Yar'. An answer to this question cites this April 1990 discussion. The 1990 discussion cites an earlier discussion dated 3/17/87. A document mentioned (cited) in both sources says about Lt. Tanya Hernandez. However, an answer to another question cites a note dated 4/13/87 where the same character is already named Lt. Tasha Yar (actually just "Tasha", but not "Tanya").
Can we assume, that Tanya Hernandez became Tasha Yar somewhere between this nearly a month long period? Or is there something else, that I'm missing?