For clock times we use at, but not usually in the question:

What time are you leaving for Germany? ~ I shall try to leave at three o' clock.

on for time

For days, dates and times like Sunday evening or Saturday morning, we use on:

I usually do my homework on Sunday evening; on Saturday morning I'm normally at the gym.

Can we do it on Thursday? ~ No, not on Thursday. I'm in Leeds all day on Thursday.

My birthday is on 26th December and then Mark arrives on 27thDecember.

(Note that we write on 27th December, but we say on the 27th of December.)

in for time

For centuries, years, seasons, months, weeks, and for time phrases such as in the afternoon, or in the evening we use in:

In the 17th Century, 200,000 people were executed in America for practising witchcraft.

Brazil first won the World Cup in 1958 and then again in 1962, but in 1966 it was England's turn.

I prefer to take my holidays in the spring and autumn and work in summer when everybody else is on holiday.

I've got my final exams in May. When in May? In the final week of May.

I work best in the morning. I'll work again in the evening if I have to, but I prefer to relax in the afternoon.

(But note we say at the weekend, at Christmas, at Easter and at night.)

Note also subtle the difference in meaning between the expressions in time (which means before a given time) and on time (which means exactly at that time):

The 7.53 is always on time, but yesterday it was late.

I couldn't get there in time for the beginning of Jo's concert and missed the opening number.

zero prepositon with time phrases

Note that usually no prepositions are used with time phrases beginning with next, last, this, every, all, any:

What are you doing this afternoon? ~ I'm busy this afternoon, but we could do it next week, if you like.

I work from home every Thursday. I'm at home all afternoon tomorrow, so any time would be convenient.

He failed to stop at the traffic lights and went through the light on red.
I was waiting for at least half an hour at the station, but no train came.
I never seem to have any money at the end of the month. ~ You shouldn't worry about that - I never have any at the beginning of the month.


on and in for place:


We use in to specify position inside larger areas such as containers, rooms, towns, countries, etc and we use on to specify position on a line or continuum. Compare the following:

I live in Ostrava. ~ Is that in Slovakia? ~ No, it's in the Czech Republic.

Have you seen my yellow T-shirt? ~ Yes, it's in the wardrobe ~ Whereabouts in the wardrobe? ~ It's on the fourth shelf at the front. ~ Did you find it? ~ Yes, it was on the bottom shelf at the back.

They have lots of family photographs on the walls on the landing, but no curtains at any of the windows.

I'll meet you at the theatre. ~ Where exactly? ~ In the foyer at 7.15.

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