In English we use a lot of prepositions to talk about time: the key questions we use are WHEN? WHAT TIME?
HOW LONG?
WHAT TIME? Only when you ask about specific times
The lessons start at 8:00
The lessons are from 8:00 to 1:50
WHEN?
At 3 o’clock At night/ at midday /at noon at Christmas/ at Easter at the weekend ( on the weekend in American English)
in June /in summer/spring in the morning/afternoon/evening in my free time
on Sunday ( on+ days of the week) on 10th June ( on+ number+month)
from………. to ( hours/months/dates)
during+ noun
HOW LONG?
for……………….. She worked in town for two hours
since…………….. She’s worked here since June
Exercises online about the use of Prepositions of Time
https://agendaweb.org/grammar/prepositions-of-time-exercises.html
http://www.english-4u.de/prep_of_time_ex1.htm
https://www.tolearnenglish.com/exercises/exercise-english-2/exercise-english-10086.php