• at：表示某一特定时间

    At night

    At 10:30 am

    At afternoon

    At the moment

  • on：表示日期

    On 6 March

    On New Year’s Eve

    On my birthday

  • in：表示月、年、世纪和更长的时间段

    In the morning/evening

    In May (month)

    In summer (season)

    In 1990 (year)

    In the Ice Age

    In the past

    In the present

    In the future