Today was the summer solstice, when the sun reached its highest point in the sky, making this the longest day of the year in the Northern Hemisphere. From here on out, the days will grow shorter.
And so, this is a fitting time for the Nativity of John the Baptist, which is celebrated on Sunday. It shows that John's declaration that he must decrease while Jesus increased was in fact chosen from the beginning to be the theme of his whole life. As John's decrease was signaled at his birth by the summer solstice, so Jesus' increase was signaled at His birth by the winter solstice, when the hours of daylight begin to increase.
Nor is that the end of the astronomical coincidences. The vernal equinox heralds the Annunciation -- when the Spring of the Incarnation dissipates the winter of hell's dominion over the world -- and of course also Easter, when new life springs up even from the grave itself.
None of this is the product of chance. The God of Order arranged it so.