Theory:

What are prepositions?
Prepositions are words that connect a noun/pronoun to verbs and adjectives in a sentence. Prepositions can be classified based on functionality.
 
It is classified as:
  1. Prepositions of time
  2. Prepositions of place
  3. Prepositions of position
  4. Phrasal prepositions
Let us study prepositions of time in detail:
Prepositions of time refers to prepositions that tell about the time of the occurrence of a particular event. It includes on, at, since, ago, until, for, during, etc.
Example:
1. I was waiting for my teacher.
2. I was born on 23rd September 2010.
3. Sheela was born in 1942.
4. The courier came at sharp 4 PM.
5. Ravi finished his homework before Ramesh.
6. I will reach home after 10 PM.
7. Since 2015, I have been working in this company.
8. I have known my friend Simi for eight years.
9. I had bread toast in the morning.
10. Within minutes, the rain started pouring heavily.
11. I gave my father a letter for remembrance until we meet next time.
12. During my summer vacation, I go to my grandparents house in Thanjavur.

The basic "prepositions of time" used generally are:

  1. at
  2. on
  3. in
  4. before
  5. after
Other prepositions of time includes "since, withinago, until, for, during" etc.
Prepositions of time used in the lesson:
  1. In the summer, he always visits his grandparents in Nagathi, a river island in Thanjavur District.
  2. My mother has instructed me not to roam in sunlight.
  3. You should use it in the presence of adults.
  4. We should first look right, left and then again right before we cross the road.
  5. Can we put on sunscreen before going out in the sun?
  6. Yes, you need to put on the Sunscreen 15 to 20 minutes before going out to avoid Sunburn.
  7. We should learn to put things back in their respective places after using them.