Look at these examples:

·                                I have a meeting at 9am.

·                                The shop closes at midnight.

·                                Jane went home at lunchtime.

·                                In England, it often snows in December.

 ·                                Do you think we will go to Jupiter in the future?

·                                There should be a lot of progress in the next century.

·                                Do you work on Mondays?

 ·                                Her birthday is on 20 November.

 ·                                Where will you be on New Year's Day?

When we say last, next, every, this we do not also use at, in, on.

·                                I went to London last June. (not in last June)

·                                He's coming back next Tuesday. (not on next Tuesday)

·                                I go home every Easter. (not at every Easter)

·                                We'll call you this evening. (not in this evening)