Preposition before 'Father's Day'

We usually use 'on' before 'Days'.

Fiona sent her dad a card on Father's Day.

Eric gave his girlfriend a big bouquet of flowers on Valentine's Day.

In China, students give their teachers presents on Teachers' Day.

However, we use 'in' before a festival.

Dragon boat racing is the a popular activity in the Dragon Boat Festival.

It is a tradtion for many in Hong Kong to gather with their family and have dinner in the Winter Solstice Festival.

We use 'at' before a festival season.

At Christmas, we can see beautiful festive decorations everywhere.

Do you know what prepreposition we should use before 'Christmas Day'?