Um, wow. That's really something you should know and understand because you want to make sure you are getting paid correctly and catch any payroll errors. They

Um, wow. That's really something you should know and understand because you want to make sure you are getting paid correctly and catch any payroll errors. They are not uncommon, I've caught a couple myself, including an $1,800 mistake. If you're paid biweekly (say, every other Friday) you have 26 pay periods. If you are paid semi monthly (say the first and the fifteenth) then you'll have 24 pay periods.