Considering how Mindfang dates her journal entries, it would be... quite odd for perigees to be as long as Earth months are.

Oooh that’s RIGHT the Journal!

The sequence goes on day by day mentioning the 16th, and up to the 20th perigees, which marks the Bilunar Perigees as days, not month, which makes more sense that this will be her last Mass(acre) on Alternia.

Which means, MSPA Reader’s arrival would either be concurrent or AFTER Joey’s arrival to Alternia, likely in a parallel reality where Joey isn’t around.