Express an action or event that occurred at a specific time in the past; 'when', 'at the time'.
Long explanation:
The たときに grammar point is used to express an action that happened at a specific time in the past, usually with a focus on a specific event or moment. It can be translated as 'when' or 'at the time' in English. This grammar point requires a verb in its た-form followed by ときに to indicate the time at which the action occurred.