Find hidden boomerangs throughout the game to unlock Bonus Days.

Unlockable	How to unlock
Unlock Day 22	Find 8 Boomerangs
Unlock Day 23	Find 15 Boomerangs
Unlock Day 24	Find 25 Boomerangs
Unlock Day 25	Find 35 Boomerangs
Unlock Day 26	Find 45 Boomerangs
Unlock Day 27	Find 55 Boomerangs
Unlock Day 28	Find 63 Boomerangs