kuya19 May 13 2022, 9:47pm CST ~ 1 week, 2 days ago.
that's what I thought but when I put your example in google translate, it translates to "He's been tired all day because of what he did this morning." I've also seen it used in other sentences meaning all day. Is there another rule of using this that doesn't make it relate to just afternoon?
As a native Filipino/Tagalog speaker, I think that both mean "whole day." I don't think there is a "strict" translation for those words.
When using "buong araw" or "maghapon" in conversations (particularly casual conversations) with us, we would understand it as "whole day." We use it often, and we interpret it as "whole day." What I mean by whole day is from sunrise to sunset.
The word "hapon" means "afternoon." So sometimes, when we hear "maghapon," we interpret it as "whole afternoon" especially if the context of our conversation is about afternoon. But generally, "maghapon" means "whole day," from sunrise to sunset.
There is no "perfect" translation. These two languages have different language rules.