Answer:
In the morning
On Tuesday morning
At the moment
On the weekend
In 2018
In winter
At 9:30
In the afternoon
On Christmas
On Sunday
In the evening
At night
In the 1990s
On my birthday
At lunch time
At midnight
On Friday afternoon
In summer
On Easter
At noon
On the weekend
Step-by-step explanation:
Enjoy some free answers, and an explanation:
Just place the three words wherever they seem fitting. As an example, what do people say when the use time markers? I'll give an example.
There is a party. 9:00.
Is it in 9:00? No.
Is it on 9:00? No.
But it is AT 9:00.
So whenever you do this again, think "what sounds grammatically correct." What do you think you would say? Because our brains can use in, on, and at correctly without realizing it. Even in speech.
For example, I wouldn't say "I'm going swimming at the weekend!" I would say "on the weekend" instead.
LONG STORY SHORT: If it doesn't sound correct it probably isn't, and you can choose a new word.