'in my school days' vs 'during my school days' vs 'on my school days'

[Zsam_Lam]

i have doubt on the usage of the word

For eg:

1. the lecture discuss, the lecture states

2 a. in my school days, i went to picnic
b. during my school days, i went to picnic
c. on my school days, i went to picnic

3 a. it is not necessary to have more than one pen in pocket
b. it is unnecessary thing to have more than one pen in pocket

[Gray]

@Zsam_Lam

i have doubt on the usage of the word

It should be – I have a doubt on the usage of few words here:

@Zsam_Lam

For eg:

“e.g.” itself means “for example”

@Zsam_Lam

1. the lecture discuss, the lecture states
   2 a. in my school days, i went to picnic
   b. during my school days, i went to picnic
   c. on my school days, i went to picnic
   3 a. it is not necessary to have more than one pen in pocket
   b. it is unnecessary thing to have more than one pen in pocket

1. The lecture discusses.

2. In my school days I went to a picnic.
   But this sounds good too – I went to a picnic when I was in school.

3. It is not necessary to have more than one pen in the pocket.
   But this sounds good too – It is unnecessary to have more than one pen in the pocket.