Regarding the birth date of Osama bin Laden, I've seen web pages that mention only a year—1955, 1956, 1957 and 1958. I've seen web pages and posts that give a variety of dates, including March 10, 1957; April 7, 1957; June 28, 1957; July 28, 1957; July 30, 1957; and October 3, 1957.

According to an interview with bin Laden, which can be found on various web pages, he himself has given his year of birth as 1377 AH (“1377 hegira”). If that is so, then he had to have been born sometime between approximately July 29, 1957 and July 17, 1958, give or take a day or so for both dates. This would mean that 1955 and 1956 are out of the question, nor can March 10, 1957; April 7, 1957; and June 28, 1957 be correct.

I think the July 28, 1957 and July 30, 1957 dates look suspicious because they are approximately the first day of the Islamic year 1377 AH. The first day of each month is tricky to determine either ahead of time, or by a computer algorithm, because it begins when the crescent Moon is first spotted following the New Moon, and this event is subject to various factors. Also, the day begins at sunset on what we would call the previous day, so if for example the first day of 1377 AH was July 29, 1957, this would mean that it actually began at sunset on July 28, 1957!

Obviously, it's possible that bin Laden was indeed born on the first day of 1377 AH. I can't help wondering, however, if the July 28, 1957 and July 30, 1957 dates might conceivably have been arrived at in the following way:
  Question: “When was bin Laden born?”
  Answer: “In 1377 AH.”
  Question: “And when was 1377 AH?”
  Answer: “On July 28 [or 30], 1957.”

As far as the other dates, I've personally seen people convert dates incorrectly from one calendar to another. For example, I used to work for a Korean-born man (whose family moved to America when he was a child) who celebrates his birthday as February 14, 1958, although he told me that he actually has two birthdays. When I asked him what he meant, he said he'd been told that he was born on the 14th day of the 2nd month of the Year of the Dog. The Year of the Dog began in 1958, so he had arbitrarily decided to celebrate his birthday on February (2nd month) 14 (14th day), 1958 (Year of the Dog). A correct conversion would put his birthday on about April 2, 1958 (depending on time zone considerations). The Year of the Dog didn't even begin until February 18, 1958—four days after the day he celebrates as his birthday!

It also should be pointed out that most Arabs use the dates when their births were registered, not the day they were born. Births can be registered months after the fact. If this is true, it implies that bin Laden's statement about having been born in 1377 AH may have actually been based on when his birth was registered. Thus, he may have even been born in 1376 AH. 

It might be possible that bin Laden's birthday—if it's even known—was incorrectly converted in such a fashion (e.g., the 10th day of the 3rd month). I would also point out the uncertainty surrounding the birthday of Princess Di's companion, Dodi Fayed. His birthday had been given as April 15, but it was stated by several people that it is a fairly common practice in the Middle East to use the 15th of the month as the birthday, due to the fact that they don't always note the actual day of birth, just the month and year of birth.

Of course, there is also the possibility that, some years ago, someone in an intelligence agency may have heard that bin Laden had just celebrated his birthday (if he even celebrates his birthday) on some day of the year, such as March 10. They may have then taken that date and used it with his year of birth, which seems to have been 1957 (or perhaps 1958). If this sort of thing did happen, it would be wrong, as a particular date (month and day) in the Islamic year does not fall on the same date each year in the Gregorian calendar. For example, if it had been learned that Bin-Laden had celebrated his 30th birthday on March 10, 1987, it would be incorrect to conclude that he was therefore born on March 10, 1957. It just doesn't work that way.

When Prince Dipendra murdered his family and shot himself, I saw some web pages which gave his birthday incorrectly, and they cited CIA sources! This makes me wonder if the “field information” gathered by intelligence agencies can be trusted, especially when it comes to people's birthdays. Additionally, there is always the chance that a Gregorian date written in numeric format might be misread, such as 3-10-1957 being variously read as either March 10, 1957 or 3 October, 1957. In light of these facts and considerations, I would be extremely cautious about accepting any date of birth for bin Laden without a grain of salt at least the size of Jupiter.