Festivals (Harvest Moon: Tree of Tranquility)
Spring Festivals
Spring 10th Flower Festival
In the first year you meet Sheila here. You can buy all sorts of flowers and herbs and also flower and herb seeds.
Spring 22nd Flea Market
In Spring and Summer, Maya, Simon, and Candace sell things. You can buy various things here, especially things like food you can't make easily or you can't buy at the inn, and items you need for the rainbows.
Spring 28th Animal Festival
You can buy dairy products here. There's also an animal judging contest.
Summer Festivals
Summer 7th Sea Festival
This is kind of a two-part thing. During the day you can buy ocean or tropical-island related food, and at night, there's a fireworks display. You can view the fireworks with one of the bachelors/bachelorettes. He or she will invite you to it the day before. They just need to be at 3 or 4 hearts or above. (4 hearts, maybe?) The fireworks display can be viewed at the beach, and it starts at 7PM.
Summer 22nd Flea Market
In Spring and Summer, Maya, Simon, and Candace sell things. You can buy various things here, especially things like food you can't make easily or you can't buy at the inn, and items you need for the rainbows.
Summer 24th Firefly Festival
This is a purely romantic one. You'll get asked to it the day before. The day of the festival, go up to the Caramel Waterfall area, and beginning at 7PM, you'll watch the fireflies together.
Fall Festivals
Fall 12th Art Festival
Mira is selling premade accessories for which you don't have to provide any ores or gems. Owen and Bo sell household furniture, appliances, and others goods that you can't find at the carpentry shop or supermarket.
Fall 22nd Flea Market
In Fall and Winter, the sellers are Elli, Julius, and Taylor. You can buy various things here, especially things like food you can't make easily or you can't buy at the inn, and items you need for the rainbows. Candace, Julius, and Taylor sell outfits or hats, too.
Fall 27th Harvest Festival
This is another one where you can buy goods, including rare seeds and crops. There's also a cooking contest. I found out that buying a dish from Elli at the fall flea market and then submitting it to Yolanda can win you first place. NOTE: It doesn't ALWAYS work though.
Winter Festivals
Winter 10th Thanksgiving Festival
Typical thanksgiving festival. You receive a sweet (usually cake) and another item (usually a flower) from bachelors (if you're a girl) or bachelorettes (if you're a guy) who like you. But if you're married, then you only get things from your spouse. And you can give cakes to other people.
Winter 22nd Flea Market
In Fall and Winter, the sellers are Elli, Julius, and Taylor. You can buy various things here, especially things like food you can't make easily or you can't buy at the inn, and items you need for the rainbows. Candace, Julius, and Taylor sell outfits or hats, too.
Winter 25th Starry Night Festival
Another purely romantic one. You go stargazing with the person you love. The person will invite you the day before, and then you meet at Aran's tree (on the Brownie Farm map) the night of the festival.
Winter 28th New Year's Eve
(Single protagonists point of view still awaiting...) If you are married, you'll automatically go home at 10PM (or, if you went to bed before that time, then your spouse will wake you up) and celebrate the new year together. You also go and watch the first sunrise of the new year together.