个人觉得：occasion后用when还是where取决于使用者把它视为时间还是场合(即抽象的地点).用法例句：
1.Please describe an occasion where you met with real difficulties.
2.In hard times, the Spring Festival was the only occasion where a family threw off the old attire and put on new clothes specially made for the festival.
3.Describe an occasion when you had to give a presentation to an audience.
4.A training session should be an occasion where the whole team works together高考的时候用什么呢？至于高考的时候用什么，没有研究过高考题，不能贸然下结论，建议你看看高考题。