Here's why:
* "Est" means "is" in English.
* "Ton" means "your" in English.
* "Jour" means "day" in English.
To make a complete sentence in English, you need more context. It likely means something like:
* "Is it your day?" (referring to a special occasion or event)
* "What is your day like?" (referring to what they are doing or feeling)
Without more context, it's impossible to provide an exact translation.