Each day has its own significance as each day of the week is for a particular tattva (element). Purification of that tattva helps getting the refined qualities in life, as our body is nothing but the mix of the tattvas. Once the tattvas are purified, they help in getting the blissful life at physical, mental, emotional and most importantly at spiritual level.

Below are the days of the week and their respective tattvas and significance:

Monday – Earth Element – helps providing grounding in life.
Tuesday – Water Element – helps providing fluidity/flexibility in life.
Wednesday – Fire Element – helps providing zest/vigor/excitement in life.
Thursday – Air Element – helps providing freedom in life.
Friday – Space/Ether Element – helps providing limitlessness in life.
Saturday – Mahatattva (Super Element) – helps going beyond the above five elements.
Sunday – Celebration day beyond mind and body, or the realization day.

Above I just wrote as one-liner, though a big chapter could be written for each element … anyway, one can also connect the seven chakras with the seven days of the weeks and their element.