The exact dates are as follows:

LeBron’s retirement is likely to occur between April and September

A 9th loss in a regular season is likely to occur between November and January

so there shouldn’t be edge cases

but to clarify, if LeBron gets a career ending injury, his NBA career ends when he’s no longer under contract with an NBA team and he states he’s played his last NBA game (applies retroactively, e.g. if CP3 says he’s retiring, now, his retirement would be whenever the Clippers cut him (December 3rd iirc)