Can my employee change the way my vacation and sick benefits accrue in the middle of my employment year.

My employement year starts August 19 of every year. When I was hired i was given 7 paid vacation days and 7 paid sick days. I receive them all at once. This is my second year working here and my employer wants to change how my time is accrued. He wants me to accrue it every pay period over the year instead of me receiving it all at once. He wants me and another guy to change it. Can he do this?