Christianity has its roots in the deep, firm soil of history. Jesus' incarnation- God invading human history with His presence in the form of man- is on the record. Every time you write the date, you attest to the fact that God entered human history.
Jesus came into the world so we might know God cares how we live, what we believe, and how we will die. Jesus came to demonstrate to us that we were made to have a personal relationship with God. He came to bridge the gap that separated us from our Creator.
" God was reconciling the world to himself in Christ, not counting men's sins against them."- 2 Corinthians 5:19