I know that when you read this question at first you're thinking what are you talking about? So let me explain: They land on earth and later awaken in 1984. And somehow years later it's 2005! The only episode that tells us it's 2000, is 'Trans-Europe Express'. And the series ends in like summer of 2006. So, where do all the episodes or battles take place on the timeline according to the G1 Transformers?
Seasons 1 and 2 take place in 1984 and 1985.
The episode 'Trans-Europe Express' also takes place in 1985. The race was called 'Europa 2000' because the course was about 2000 miles.
Then, 'Transformers: The Movie' occurs in 2005, 20 years after season 2.
Season 3 takes place shortly after 'The Movie' and season 4 (just one 3-part episode) ends in 2007 (according to the transformers wiki).
You can notice the 20 year difference because Spike is a boy during the first two seasons but a grown man during season 3.