Warning: mentions of animal death. Sorry. Also the timeline is based off my observation of it being mentioned that Donald was the same age as my mom on one of the earlier seasons. Which brings up the question of how quickly was Douglas able to create the rats. I don't believe he used accelerated aging technology for the rats, but he had to have gree them in pods.
16 is the worst year of Donald's life.
In January, there is an unpredicted blizzard and the power goes out. It remains out for several days. Even with everything they do, the first foal of the year 1990 does not make it.
In February, Donald's favorite barn cat gets hit by a car. He discovers her after looking for her for two weeks. He spends several days crying in Belle's stall.
In March, Douglas falls off a horse that his father had warned him was too green and breaks his arm. All Donald says is "We told you not to mess with her."
In April, his father passes away from an accident during a race. The funeral is not lavish, just catered by the nearest grocery store's deli, but it is large and loud.
In May, his mother is diagnosed with cancer. They hope it's caught early enough. But the way this year is going, hope is futile, Donald thinks.
In June, the pipes for the sprinklers burst, flooding several of the pastures.
In July against his mother's wishes he goes to science camp there he meets Amy Reinhart a brilliant blonde who talk his ear off anytime she wants she listens to all of his ideas that he's willing to share but he would rather listen to her they share a kiss by the bonfire on the last night but the next morning she's gone he has her number but he can't visit her because she lives hours away.
In August, all of Donald's fish die. He never figures out why or how they survived the big freeze yet randomly die on a normal day. Although, secretly, he expects that it is a result of one of Douglas' bizarre experiments.
In September, Donald's father's beloved horse colics, and has to be put to sleep. Donald thinks he was more upset than Douglas or their mother.
One day in October, Donald wakes up with a horrible stomach ache. His mother forces him to do all the morning chores anyways. He passed out in the field. He wakes up once to Belle licking his face, the second time days later in the hospital.
In November, their grandfather's house catches on fire. It appears to be electrical, how fast it spread, but the exact cause cannot actually be determined. He develops pneumonia from smoke inhalation since he kept moving all the animals the furthest away from the house as he could while waiting for the fire department. He lives, thankfully, however his immune system will be weakened for a long time.
In December, Donald turns 17.