Prepositions of Time - at, in, on

We use:

• at for a PRECISE TIME
• in for MONTHS, YEARS, CENTURIES and LONG PERIODS
• on for DAYS and DATES

For years, months, seasons, centuries and times of day, use the preposition in:
 - I first met John  in  1987.

1. BUILD YOUR VOCABULARY

Work on building your vocabulary every day by choosing new words to learn and repeating each word over and over to reinforce the memory of those new words.

These are materials made up by the general English teacher and they can used to make your english writing and speaking much more fluently.

https://www.fluentu.com/blog/english/esl-english-grammar-mistakes/