It had to start sometime. If by start you actually mean end, that is.
The northernmost point in the bowl of Aevum only sees the sun once every 2,000 years, and even then it only drifts near enough to spill a few hapless rays before remembering itself and backing away in embarrassment. Not that it does any good; the meager rays left behind freeze before they even reach the ground. Everything freezes instantly here, even the intangible. Dotting the borders of this land are small specks in the sky, their wings spread, frozen forever in the final arc of flight as they flew too near the edges of the Temporal Ice Plains.
These are the rimebirds, the only creature in the known universes to have developed a circulatory system with anti-freeze. For daring explorers out to see the famous northern lights, their ominous final flights marked the no-go zone, where the Ice Plains begin and even time itself freezes. Should anyone have been able to survive a trip across the plains they would have seen pockets of time holding humans and even strange creatures from the furthest reaches of time and imagination in terrifying statuesque scenes. They had been frozen in the early days when the temporal freeze was still expanding, laying unseen traps for those who hunted and lived near the once-habitable plains. It had been a storm that lasted millennia, one with all of the power of a hurricane and the haste of mountains. But the boundaries had been stable for centuries now, the birds on its fringe anywhere from dozens to hundreds of years old.
High above the blue expanse of the plains, facing south toward the sun were it not so far away, was the tiniest ruffling of white feathers. This was followed by a larger rustle as a wing caught wind for the first time in decades, and followed further by the squawking of a bird with some very confused memories and stiff wings as it fell away from the borders of the Temporal Ice Plains. Further away, another white dot wheeled similarly away from its prison in the frozen pocket of time.
Unseen, a few strands of belated time uncurled from the fringe like lazy smoke and drifted out into the world.
Winter was ending. Something new was beginning. Something new, and also something very old.