(....的时候de shi hou ) is similar to "when" For example: (1)when i think something seriously ,i am unhappy to be disturbed. 当我认真思考的时候，我不高兴被打扰 (2)when we have interviews,we will be a little nervous 当我们要参加面试的时候，我们会有点紧张 (3)when we will have business travel ,we should do some prepartions ahead of time,such as booking tickets,hotels and so on. 当我们要商务旅行时，我们应该提前做准备，比如订机票，酒店，还要其他。

我给你举几个例子吧，比如说：我想你的时候，我哭的时候，我吃饭的时候，我睡觉的时候。说明这个时候你在干什么。

“英语的语法顺序和中文的语法顺序有时候是相反的”在这里就体现了。"I will go to class when I can"里的从句部分"when I can"翻译成中文应该把when和I can掉个头：我可以的时候。而且，整个句子翻译成中文时最好也要掉换一下语序：当我可以的时候我会去上课。 另外我感觉你的提问提得不是非常准确，中文里面“的”的用法还有很多，你提出的只是其中一个。

的+时候.. meaning "when/while" is placed after the event you're talking about, i.e. "When I was eating" 我在吃饭的时候 as opposed to in English where "when/while" would be placed in the beginning of the sentence. Sometimes you might see 当....的时候，当我在看电视的时候，她一直在讲电话　-she keeps talking on the phone while I am watching t.v. To make things easier, you can also [informally] just use 时 alone: 我打篮球时- when I play basketball. It's also used in a question such as: 什么时候?(when?) 你的生日是什么时候？-When is your birthday? 他什么时候回来？-When is he coming back? Its generally used to talk about a time that happened before now or in the past: 那时候，我很紧张　"at that moment I was so nervous." 有很多时候，我不喜欢他-there are many times where I don't like him. As for ’我会上课的时候我可以‘ i'm not sure this is correct. It means "When I will go to class, I can". 会 and 时候 don't make much sense together in this sentence. I think a better way to say that would be: 我能去上课就去-when I am able to go to class [then[ I will go.Its very different from the English way of saying it, but Mandarin and English are spoken in two totally different ways.

‘的时候’means a time point.When you think the time is right to do something,like I think I should go to bed now.In Mandarin you can say:我想现在是睡觉‘的时候’了。