at---1)用在確定的時間之前，如 at midday ;at midnight; at 3 oclock . 

      2)用在短的假日期間。如 at Christmas ; at Easter ; at the weekend

      3)用在所指定的短時期前。如 at the end of January; at the beginning of the year.

      4)用在吃飯時間之前。如at breakfast, at lunch, at dinner

      5)用在我們說的夜晚時候，及每個夜晚。如 at night, at each night。 但要注意，當我們指的是某個時間的一半時，則要用 in the middle of ……

 而當我們說的是一個特定的晚上時，用 in the night. 如：

         I felt very restless at night and had to take a sleeping tablet.

      6)特定用法：at the moment = now 和 in a moment = in a short period 例子：She is in Taiwan at the moment.

                       Ill be with you in a moment.

in----1)用在指四季，月份，年份，某個十年(decades　如1990s ), 世紀(如16th century)和其他如.. in the week before Easter, in the hours before the exam

        2)用在指一段時間之後，如 In a few minutes, we will be arriving at Taipei Airport.

      3)用在指某事所需的時間，如 He learned how to cook Chinese food in two weeks.

      4)用在指一天當中的某段時間，如in the morning, in the evening(但記住---at night!)

     5)在未來的一段時間也要用in，如兩年後我就20歲了。

        Ill be 20 years old in two years.

on----用在指特定的某一天，日期，及特定日子的某段時間。如：

       on Friday, on the 21st, on the last day of the month,

       On Easter Sunday, on Monday morning. On Christmas eve

       On Christmas night.

Dec.15, 2018 當年這篇文章花了我老大一口血，但是來轉傳的，來參考的人，從未說過一聲謝，還以為是我從別的地方轉過來的吧？不過沒關係，算命的說我「桃李滿天下」大概就是這指這篇文章造成的影響吧？