How to Remember Prepositions IN and ON when you Speak English

source: Go Natural English   2015年2月6日
One common mistake is to use the wrong preposition when you're talking about a year, month or day. Remember that when you say only the month, use "in March."
If you say a month and a day, use "on March 20th."
I saw that I had a plastic container full of tomatoes in my kitchen. So, I decided to explain how to remember this grammar point thinking about the tomatoes. See, the tomatoes are like days and the plastic box is like the month. The tomatoes are in the box. So, we say "in March" as if the month were a box full of days -- or tomatoes.