当我们学习英语语法时，定语从句是一个非常重要的部分。在定语从句中，when引导的定语从句表达的是时间关系，下面是20个when定语从句的例句。

1. The time when we first met was unforgettable.

2. Do you remember the day when we went to the beach?

3. I like to listen to music when I'm feeling stressed.

4. The moment when the sun rises is always beautiful.

5. The time when I first saw her, I knew she was the one.

6. The day when we got married was the happiest day of my life.

7. I always feel sleepy when it gets dark.

8. The time when I finished my project was a relief.

9. The moment when I heard the news, I was shocked.

10. The day when we went to the amusement park was so much fun.

11. I always feel hungry when it's time for lunch.

12. The time when we were lost in the forest was scary.

13. The moment when I saw the accident, I called for help.

14. The day when we won the championship was a dream come true.

15. I always feel happy when I'm with my family.

16. The time when I graduated from college was a milestone.

17. The moment when I received the award, I was thrilled.

18. The day when we visited the museum was educational.

19. I always feel cold when it snows outside.

20. The time when I traveled to Japan was a cultural experience.

这些例句展示了when定语从句的不同用法，可以帮助我们更好地理解和运用这种语法结构。当我们学习英语时，了解和掌握定语从句的用法是非常重要的，因为它们在口语和书面语中都非常常见。