'fatal day' is correct and usable in written English.
You can use it to refer to a day that has had disastrous consequences, either literally or figuratively. For example, "The day of the financial crash in 2008 was a fatal day for many businesses."
I went to Hiroshima some three weeks after the fatal day.
He said the force believed two firearms were used on the fatal day, a pistol and an automatic weapon.
But since the fatal day when he was ordered to withdraw his enthusiastic acceptance of the offer of the Marshall Plan he had been a changed man.
Life is uneventful until the fatal day of the Epsom Derby, the day a young Emily Davison throws herself in front of the King's horse.
That is indeed the impression that Ms. Lamia gives as the daughter tells her own story of a lost mother and a fatal day at the beach or sinks into the dubious comforts of a threadbare romance novel.
Hours before sunrise on the fatal day, the Mendi was motoring slowly through a thick fog, escorted by the British destroyer H.M.S. Brisk, which provided protection from German U-boats and mines.
They have the effect of bringing that fatal, fateful day much closer than it might otherwise be.
Read said the lesson from the fatal 2009 Black Saturday bushfires was less about planning than about ongoing support.
Because of the age of the houses, few complied with the Australian building standards for bushfire safety, which were updated to include recommendations from the royal commission into the fatal 2009 Black Saturday bushfires.
Mr. Hubbell, in his book, writes that his father-in-law's impatience was nearly fatal one day in 1989.
What makes these figures so glaring is that they run counter to an overall decline in fatal race-day injuries.
