Periods of time
EXAMPLE:
In morning
In afternoon
In the evening

OF.
Days of week
EXAMPLE:
On monday
On Tuesday
On weekend 
On Weekday

AT:
Times, noon/night
EXAMPLE:
At 8 o´clock
At night
At 10 o´clock

FROM... TO:
Days, months, times, years
EXAMPLE:
From 6 to 8
Fom monday to friday
From february to June