Looking on the internet deeply has found these results:

in April is the most popular phrase on the web.

on April 123,600,000 results on the web	in April 1140,000,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
Renée Zellweger Actress, Bridget Jones's Diary Renée Kathleen Zellweger was born on April 25, 1969, in Katy, Texas, USA. Her mother, Kjellfrid Irene ... Jordana Brewster Actress, Fast Five Raven in April, the 10th; in April 10th; on April 10; on the 10th of April; any other? I usually use the first one, but I think also the fourth one is correct. haired beauty Jordana Brewster was born on April 26, 1980 in Panama City, Panama. Her mother, Maria João (Leal ... Hi! I would like to know wich one it´s the correct answer: In April or On April? And in this sentence? on the 2nd of April or in the 2nd of April?	The US An ex officio case was therefore opened in April 2007. led project was launched in April 2006. Italy and Austria transposed the Directive in April and June 2003 respectively. The programme indicates as well that new measures aimed at reducing central government spending will be presented in April. Sachiko just started school in April. My husband Emilio passed away in April.

on April

123,600,000 results on the web

in April

1140,000,000 results on the web

More popular!

Renée Zellweger Actress, Bridget Jones's Diary Renée Kathleen Zellweger was born on April 25, 1969, in Katy, Texas, USA. Her mother, Kjellfrid Irene ...
Jordana Brewster Actress, Fast Five Raven
in April, the 10th; in April 10th; on April 10; on the 10th of April; any other? I usually use the first one, but I think also the fourth one is correct.
haired beauty Jordana Brewster was born on April 26, 1980 in Panama City, Panama. Her mother, Maria João (Leal ...
Hi! I would like to know wich one it´s the correct answer: In April or On April? And in this sentence? on the 2nd of April or in the 2nd of April?

The US
An ex
officio case was therefore opened in April 2007.
led project was launched in April 2006.
Italy and Austria transposed the Directive in April and June 2003 respectively.
The programme indicates as well that new measures aimed at reducing central government spending will be presented in April.
Sachiko just started school in April.
My husband Emilio passed away in April.