Considering your application as early as possible is the best way to go. After all, the sooner you gain acceptance into a university, the sooner you can arrange your travels. To avoid disappointment, note down all the relevant application deadlines (set out by your chosen university) in HUGE LETTERS on your calendar.

Application deadlines will be different depending on the school, but generally speaking, for programs starting in the fall (September/October), applications will be open from early in the year (January/February) until the middle of the year (June/July).