How Long Would 30% Glycolic Take to Even a Dark Uneven Skin Tone?

i am supposed to have brown skin and so does everyone in my family but after a summer of being in the sun almost all day from work my face and neck has become darker than the rest of my body,ive used some lightening creams but they just dont seem to be working fast enough, my face is dark brown now with the skin around my eyes and near my ears being lighter than the rest of my face, what percent of glycolic would work fastest for a dark african american skin? i need it to be more even