Everyone: Below is an explanation that has come from Track & Field New staff. In 1998 there was a change. I can see both sides of the equation, only letting those marks count that end with the NCAA Championship, and letting marks count throughout the summer. I keep two lists given this dilemma.
DATES OF RANKING: Until 1998 college bests performances were allowed to count from the first collegiate meet an athlete competed in their freshman year until the end of August following their senior year. In 1998 that changed to outdoor performances are only allowed from March 1st of each year until the completion of the NCAA Outdoor Championships that same year.