To translate it, you need more context. It's likely part of a sentence or phrase. For example:
* Quand ton train arrive ? (When does your train arrive?)
* Quand ton anniversaire ? (When is your birthday?)
* Quand ton film commence ? (When does your movie start?)
So, depending on the context, you could translate "quand ton" as:
* When your...
* Your...when...
For a more accurate translation, please provide the full sentence or phrase containing "quand ton".