#Bash +GNU date, <s>72</s> 73 bytes

    for((d=0;1`date +%d%m -d$d\day`-12512;d++));{ x+=\ Eve;};echo Christmas$x

- one byte saved replacing `!=` with `-`
- another removing extra space
- fix -3 bytes `d=0`, because `date -dday` is date+1 and doesn't work on 25/12

[Try it online][1]



  [1]: https://tio.run/##S0oszvj/Py2/SEMjxdbA2jAhJbEkVUFbNUU1V0E3RSUlJiWxMkHX0MjU0Mg6RVtbU9O6WqFC2zZGwbUs1brWOjU5I1/BOaMos7gkN7FYpeL/fwA