Halloween
On/At Halloween
Easter
At Easter
1st of January
On the 1st of January
21st century
In the 21st century
1969
In 1969
20th century
In the 20th Century
2004
In 2004
Autumn (or fall)
In autumn (or fall)
a public (or bank) holiday
on a public (or bank) holiday
summer
In summer
noon (midday)
At noon (midday)
my birthday
On my birthday
Valentine's day
On Valentine's day
spring
In spring
