October 10th, the day the tragedy occurred.
Minato Namikaze, the Fourth Hokage, and his wife, Kushina Uzumaki died that day. The nine tailed fox attacked the Leaf Village, being Hokage and that being his duty, he gave up his life to protect the village and its inhabitants.
After all, his wife was the jinchūriki of the nine tailed fox.
For female jinchūriki, the seals containing the tailed beast are at their weakest during childbirth, due to the nurturing of the child in the womb taking precedence over the reinforcement of the seal. The extra precautions they took ended up failing. A man dressed in a black hooded cloak, wearing a white mask with black swirl patterns and a single hole for an eye, somehow drug out the nine tailed fox from within its host and made it attack the Leaf Village.
The dreadful night came to a close when the Fourth Hokage resealed the nine tails into a newborn baby. His and Kushina's newborn son, Naruto. But in the process, he and Kushina both died.
That was almost thirteen years ago...