PREPOSITIONS IN, ON, AT.

A preposition is a word or groups of words used before a noun or a pronoun to show place, position, time or method.
 Preposition in usage with periods of times and places.
Examples:
• Months = in April
• Seasons = in winter
• Country = in Greece
• City or town names = in New York
• Times of the day = in the morning, afternoon, or evening.
Exception: at noon, at night
 Preposition on usage with specific days.
Examples: on Friday, on New Year’s Day, on April 16
Note: American English = ‘on the weekend’ or on ‘weekends’
 Preposition at usage with specific times and specific places.
Examples: at 7 o’clock, at 6.15, at night, at school
Note: British English = ‘at the weekend’ or ‘at weekends’