Christmas is not an event within history but is rather the invasion of time by eternity. (Hans Urs Von Balthasar)
Eternity Is Not Linear
From our point of view, the Infant Jesus was born in a moment in history more than 2,000 years ago. People see time as linear, measurable and so view the first Christmas from theirr point of view as creatures who are bound by time. This egocentric view completely misses the real ramifications of the Incarnation in our lives.