EWTN Catholic Q&A
Question from Bill Anthony on 01-24-2014:

Why does my rosary brochure suggest saying the mysteries on certain days of the week during most of the year and changing those days during lent and advent?

Answer by Richard Geraghty on 01-30-2014:

Dear Bill,

The Church has a vivid sense of the passage of time. Just as the year moves through it four seasons, so the Church moves through the time before and during the coming of Christ. Our redemption is hooked up with time. Hence the different seasons of the year and the liturgy make a difference in our understanding of the mysteries involved.

Dr. Geraghty