Many people that have foreseen future events such as Nostradamus were beloved to have tapped into a ephemeral time stream. In essence, the time stream is like river flowing in all directions. Instead of water, events and portents of the past and future are constantly flowing.
Certain people have the ability to connect with this stream and pluck out events. They don't have much control and the glimpses they get are fast and fleeting, so they are left with only pictures in their head and a need to decipher it.
Nostradmus did it with quatrains that still vex those who try and understand them. Many people connect only a few times in their life and are left with strange prophetic dreams that eventually come true. It could be as simple as a future birthday party of some person they have never known or a plan crash three years down the line.
Many people consider time to be something that can bent. Even Einstein believed that time is dependent on the perspective of the person. Two people can experience time in a completely different way.
Of course, the time stream is just a theory like all things involving psychic phenomena it is unproven and untested. There is no river in the sky flowing with memories and future events, but that doesn't mean it isn't there. The future is a fickle thing and if there is a universe for every decision we make, what makes us think we can't tap into these forces.