I am a day both bold and bright,

Marking the end of a long, tough fight.

When tanks rolled in and flags were high,

The South and North saw the same sky.

I come in April, year seventy-five,

And ever since, hope came alive.

Now fifty years have passed, hooray!

What historic day am I, I say?

 Answer: Reunification Day (April 30, 1975)