Fear of Friday the 13th is less commonly known as friggatriskaidekaphobia but appears to be one of the most hated days.  I don't know where this superstition came from, or why.  But, I can name a few days that can compete with it...

Valentine's Day - imagine being a member of the Knights Templar who had been marked for assassination on February 14th and finding out about it in time to save yourself but none of your dearest friends?

Any Monday!

The day before pay day!  Yes, because you can guarantee that you're overdrawn at the bank and your friends from work are collecting for another friend who's celebrating their birthday and you feel obliged to chip in.

Christmas Day...  I know, we all enjoy the food, but every bloody year it gets more and more expensive and are the family arguments really worth it?

Your birthday, because you're another year ruddy older and have nothing to show for it... Again!

Bring on Friday the 13th... I'm bloody well ready for you!