The first line of The Stranger goes like this:
Maman died today. Or yesterday maybe, I don't know. I got a telegram from the home: "Mother deceased. Funeral tomorrow. Faithfully yours." That doesn't mean anything. Maybe it was yesterday.
Meursault doesn't know exactly what day his mother (Maman) died.
In this opening, he reiterates the same point a couple times - "Or yesterday maybe", "Maybe it was yesterday". That, combined with "That doesn't mean anything", is hinting to me that perhaps it's not sitting quite right with him that he doesn't know what day she died.
Is Meursault bothered by the fact that he doesn't know what day Maman died?