You can propose before summer, but you can't get married. You have to wait until the end of the year.
In Another Wonderful Life and A Wonderful Life, you can't buy them. They will come to you in the summer after you get married if you have the pond.
Orange and Banana Trees.
In Harvest Moon: A Wonderful Life Muffy does not have a birthday. Nobody does. In Harvest Moon DS Muffy's Birthday is Summer 5th.
Summer! If I may, I suggest you get a seed maker and make banana seeds. They sell for HIGH prices ;)
In Summer Nik, Nak, and Flack will find a Blue Feather and give it to your character.
You cannot get a white horse only a light brown one in the Summer time.
you have to buy a chicken in the second year on the first day of summer in the second year you will get your horse.
In Summer of your first year Nik, Nak, and Flak will give you the Blue Feather.
Takakura comes to you within the second year and has te horse i believe that it happens around summer of fall.
To use the fireworks in Harvest Moon: Another Wonderful Life, you need to purchase them from Van on the Van's Store on the 3rd of Summer. Then on the night of the Firefly Festival, which occurs on the 7th of Summer, go to the beach and use the fireworks by pressing the A button when standing on the pier to set them off. This will trigger a cutscene showing the fireworks display.
In any year on the first day of Summer go to Gustufa's house for the Summer festivle. On year two and so on, on Fall 5th go to Romona's house for the Harvest festivle. I only know of these two. I hope I helped! :) -love your friends and you might get rewards! ;)
Pres. Grant got married in the summer of 1848, more than 20 years before his presidency.