Is the Android Saga's timeline changes confusing you? Well here's a little help!
Behold! The DBZ Timeline!!!
ORIGINAL TIMELINE:
Goku dies from heart disease.
One year later, Androids 17 and 18 appear, killing all Z Fighters except for Gohan and the Newborn Trunks.
17 years in the Future, Gohan is killed in battle. Trunks finally transforms and goes back in time to warn the Z fighters.
CELL'S ALTERED TIMELINE:
Goku still contracts heart disease, but it's one year later than before. He also makes a full recovery.
All Z fighters survived.
Cell arrived and absorbed both Androids. 18 was eventually restored.
Gohan became the first to Super Saiyan 2, destroying Cell.
17 years in the future, Future Trunks returns and defeats Androids 17 and 18, but is killed by Cell.
TRUNKS' ALTERED TIMELINE:
Same as above, only in this one, Trunks had the Ultra Super Saiyan transformation when he returns. As a result, he defeated Cell and became the strongest fighter in the Universe.