Grammar Guide: Prepositions of Time

Every four years, one extra day is added to the Gregorian calendar in order to make our calendar year aligned with the astronomical year. Normally, a year has 365 days; however, since it takes a few hours longer to get around the sun than that, we add an extra day to our year. On a leap year, a year has 366 days.

Prepositions of Time

Prepositions in English are some of the hardest words to learn because many prepositions are idiomatic and don't necessarily follow grammar rules. There are, however, some rules that make remembering prepositions easier--but there are many!

Today we will discuss the prepositions of time in, on, and at. 

In

We use the preposition in for centuries, decades, times of year, months, and general times of day.

• Leap year originated in the time of Julius Caesar. 
• There was no leap year in 1900, but there was a leap year in 2000.
• Leap day occurs in February because it is already the shortest month.
• Janet forgot about leap day until she arrived at the bank in the afternoon.

On

We use the preposition on for calendar dates and days of the week.

• Leap day will occur on February 29, 2012.
• This year, leap day is on Wednesday.

At

We use the preposition at for clock times and specific times of day.

• When I woke up at 5 a.m. this morning, I thought it was March 1.
• I found out that it was still February when I talked to my friends at lunch.

Exception! The preposition at is also used for night, even though night expresses a general time of day.

• We read about the history of leap year before going to bed at night.

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