I'm not 100% sure on this, but i beleive it went something like this :

Black Heart Event :
Monday Wednesday, or Friday
12 noon to 3pm
Must be sunny weather
At the beach

Purple Heart Event :
Monday, Wednesday, Thursday, Saturday or Sunday
11am-4pm
Must be a Rainy day
Rock must be at 10 000 LP(Love Points) or higher
In the Inner Inn's lobby

Blue Heart Event :
Tuesday
1pm-5pm
Must be a sunny Day
Rock must be at 20 000LP or higher
The past to Goddes pond

Yellow Heart Event :
Any Day
6am-11am
Rock must be at 40 000LP or higher
In Rock's bedroom, second floor in the Inner Inn