How to use On/In/At (time)?

A. Principles 

We use:

AT for the time of day:

• at six o’clock               at 11.15          at midnight   
• at lunchtime                at noon           at sunset                    etc…

ON for days a and dates

• on Monday/ on Mondays                 on 16 October 1989             on my birthday 

IN for longer periods (months/ years/ seasons)

• in October                  in 1989                      in the 21^st century                in the past
• in (the) winter            in the 1960s              in the Middle Ages               in (the) future

B. Notes:

1. We says:

 in the morning(s)/afternoon(s)/evening(s)

BUT     on Monday morning(s)/afternoon(s)/evening(s)

2. Expressions:

we use at:

            at night          at the weekend/at weekends        at Christmas

at the moment/ at present                        at the same time.

We use in: say how long it takes to do something.

            In a few minutes                  in six month                         in a week      

Next lesson we will learn more detail about ON/IN/AT using with “time” and in position.