Could you tell me the difference between Over and During when they're placed before time?
For example,
He worked very hard during the five years.
He worked very hard over the five years.

Question

Answer

hello! good question!
over  means "period of time"
for example
i have known you over 10 years"i have known you more than 10 years"
but during "similar to when"
for example 
during watching tv,the phone rang 
hope this helps