A
____ January
In January
____ 2018
In 2018
____ the evening
In the evening
____ 2017
In 2017
____ night
At night
____ midnight
At midnight
____ weekdays
On weekdays
____ the morning
In the morning
____ Spring
In Spring
____ 3 o'clock
At 3 o'clock
____ an hour
In an hour
____ dinner
At dinner
____ 5 o'clock
At 5 o'clock
____ Monday
On Monday
____ Summer
In Summer
____ the weekend
At/On the weekend
In British English is "at"
In American English is "on"
____ December 1st
On December 1st
____ October
In October
____ Tuesday morning
On Tuesday morning
____ Valentine's Day
On Valentine's Day