Published histories disagree and none read was the Maharashtra Forest Department notification. Krishnagiri National Park is dated 1942 (Bombay National Park Act) by Mumbai Tourism and IndiaGeographies, 1950 by WorldAtlas, 1969 or 1974 for the Borivali name or expansion, 1976 by WorldAtlas, 1981 for the renaming after Sanjay Gandhi by most sources, and 1996 by WorldAtlas and Mumbai Tourism for the same renaming, with IndiaGeographies giving national park status as 1983.
What would resolve this The Maharashtra Forest Department or Government of India notification text or the park official history page, stating which year each step (Krishnagiri National Park, Borivali National Park, Sanjay Gandhi National Park) took effect, so the page can state one establishment year and the recorded fact can match it.
OpenSanjay Gandhi National Park (Wikipedia)