A time-word or -expression is normally placed either after the subject or at the beginning of a sentence:
我們十點半上中文課
十點半我們上中文課
Some notes:
A time-word does not take a preposition:
我三點下課
but not 我在三點下課
A time-word should not be placed at the end of a sentence:
她晚上來
She came in the evening.
or 晚上她來
but not 她來晚上
If you have more than one time-word, the bigger unit goes before the smaller:
今天晚上八點
at 8 o'clock this evening
If you have both time-word and place-word, usually the time-word goes first:
我晚上八點在圖書館等你
你哥哥現在在哪兒工作﹖
明天你幾點在哪兒上課﹖
When and where are you going to have your class tomorrow?
Time-word + 的 + noun (time-words modifying nouns)
A: 你想看幾點的電影﹖
What show do you want to see? /literally/ What time's film
do you want to see?
B: 我想看中午十二點半的(電影)。
I want to see the film at 12:30 at noon.
A: 這是今天的報嗎﹖
Is this today's paper?
B: 不是今天的報﹐是昨天的。
It isn't today's paper, it's yesterday's.