Time is flexible: the same amount of time can feel long or short. Happy years fly quickly but anxious days creep by slowly. My 13 happy years so far in Arkansas seem like a single day.
This is the beginning of Advent, which has two parts because it's a time of waiting for two comings of Jesus — his second coming at the end of time and his first coming at Christmas. In Advent time is flexible. For instance, the fourth week of Advent seldom lasts a full seven days! When Christmas falls on a Monday the fourth week of Advent is just a single day.
In a similar way, the two periods of history that Advent represents are also flexible — at least from the perspective of those who are doing the waiting. The Jews had waited for the Messiah for 500 years, but when he came, they were still unprepared: Jesus wasn't anything like they expected and so even today most Jews are still waiting. Their ongoing Advent has already lasted 2,500 years and still counting.
“If you are vigilant and pray and act, not to worry: you’ll be ready for the Lord when he comes. But if you don’t, watch out! That day will catch you by surprise like a trap.”