Friday the 13th

Many people are very superstitious about Friday the 13th.  The fear of the number 13 is called triskaidekaphobia.  The fear stems back to several different unfortunate events that have been assumed to have happened on that particular day.    
"There is also a biblical reference to the unlucky number 13. Judas, the apostle said to have betrayed Jesus, was the 13th guest to the Last Supper.
As for Friday, it's well known among Christians as the day Jesus was crucified. Also, some biblical scholars believe Eve tempted Adam with the forbidden fruit on Friday. Perhaps most significant is a belief that Abel was slain by his brother Cain on Friday the 13th." (National Geographic)
It's hard to say whether or not these events happened on these days.  Maybe it's just coincidence, but I'll just believe in the things that we know from the scriptures.  We know that prophets throughout the scriptures used symbolism to teach about Jesus Christ and that the meaning behind the numbers can be used as symbols as well.  Some of the scriptural symbolism behind the numbers are listed below:

Number	Scriptural Symbolism
1	God, Genesis, beginning
2	Christ, opposition, deliverance
3	Holy Ghost, Godhead, solid, divine protection
4	Earth (North, South, East, and West; 4 elements; divisions of day; seasons, and etc)
5	Grace (4+1)
6	Man’s imperfection (6 times, Savior is charged with having a devil inside, serpent in Hebrew has 6 names)
7	Oath, spiritual perfection
8	Abundance, Covenant, beginning, new
9	Judgment
10	The Law, Order (10 Commandments)
11	Discord, disorder (12-1)
12	Priesthood authority, governmental perfection (quorum of 12 holds all Priesthood keys)
20	Expectancy (i.e. 20 years Jacob waited to get wives and payment)
30	The right moment
40	Probation, trial, renewal (40 days ark)
200	Insufficiencies