在月份前面用in还是on

　　例句：

　　In March and April, the weather is much less predictable.

　　三、四月份的天气非常不好预测。

　　The rocket was launched in March 1980.

　　这枚火箭发射于1980年3月。

　　It was five o'clock in the morning.

　　那是在早上五点钟。

　　I want to make an early start in the morning.

　　我想早上早点出发。