The use of humor that Basheer employs in "Birthday" is to present a reality diametrically opposed to the conventional understanding surrounding one's special day. The opening to the story where the protagonist rises early fulfills the perception about one celebrating their birthday. The protagonist rises early and gets ready. The natural inclination is that he rises early in commemoration of his birth. Here begins what seems to be a traditional idea of one's birthday and how it is a perfect day.
Examining a reality contrary to this is where the humor lies in the story. It is humorous because in seeing all that the protagonist endures on his special day, one recognizes that the traditional notion of a birthday might be a bit faulty. The humor lies in the misguided nature of traditional ideas. The protagonist's experience does not make his birthday any different than any other day. The protagonist struggles for food and basic money on this day as any other day. The humor lies in having to reevaluate how birthdays are perceived. For those who are wealthy, birthdays can be a special day, filled with presents and food galore and a day in which people can "guard against any misdeed." The protagonist speaks to this condition of being on his birthday: "I must not borrow from anyone today. Nothing must go wrong on this day."
There is a particular sadness in the protagonist's struggle to simply live on this special day. The humor that exists is the reevaluation in how we see birthdays. For some, a birthday is no different than any other day. The struggles that life presented the day before are the same that life will present on one's birthday. These are the same struggles that will be present the day after. Humor exists in this realization. The ending of the story where the protagonist has eaten and is full is his gift to himself on this "special" day. It is a struggle that will continue tomorrow and for the days afterwards. In recognizing that a birthday might not be special after all is where there is humor lies.