Looking on the internet deeply has found these results:

at the end of March is the most popular phrase on the web.

on end of march 1390,000 results on the web	at the end of March 122,100,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
It doesn't look like this phrase is very popular! The search could not find any examples on the internet.	Linda and Christopher Cavanaugh died in the fire at the end of March. The EU This inexplicable radar phenomenon occurred once more at the end of March 2006. Cover expires at the end of March. And a similar message was also communicated at the foreign ministers' informal meeting in Slovenia at the end of March. Nevertheless, FMD spread very quickly in the following weeks, particularly in Northumberland, Cumbria, Devon, Wales and Scotland, reaching a peak of around 50 outbreaks a day at the end of March 2001. Western Balkans forum which is to take place in Slovenia at the end of March will be very important in this context. All previously existing AOCs were suspended at the end of March 2013.

on end of march

1390,000 results on the web

at the end of March

122,100,000 results on the web

More popular!

It doesn't look like this phrase is very popular! The search could not find any examples on the internet.

Linda and Christopher Cavanaugh died in the fire at the end of March.
The EU
This inexplicable radar phenomenon occurred once more at the end of March 2006.
Cover expires at the end of March.
And a similar message was also communicated at the foreign ministers' informal meeting in Slovenia at the end of March.
Nevertheless, FMD spread very quickly in the following weeks, particularly in Northumberland, Cumbria, Devon, Wales and Scotland, reaching a peak of around 50 outbreaks a day at the end of March 2001.
Western Balkans forum which is to take place in Slovenia at the end of March will be very important in this context.
All previously existing AOCs were suspended at the end of March 2013.