Here's where I draw the line:
Is it sin? Are the ways I celebrate the holiday a sin? Am I giving praise and worship to something other than God? Or am I spreading God's love as I go about the events during this day? Are the events sinful? If not, then who are you to tell me I can or cannot? Do I not also have the Holy Spirit dwelling within me? If I am actively seeking Him, will he neglect to inform and convict me of my wrongs? If He does not convict me, who are you to do so? Are your ways higher than His? Unless you can explicitly show that celebrating a holiday is a sin, then this falls under personal conviction.
Signed, the girl who just celebrated Purim and can't wait to celebrate Pi Day here in 11 days. Because God created math. And everything that goes into pie. And we will be sharing His goodness with children and unsuspecting adults. I'm already planning my Pie-bys - closely related to the drive-by, but where you deposit sweet pies on peoples porches, ring the doorbell, and run.
(If you read any of this in an argumentative tone, please re-read it in a more "eh," nonchalant way. I'm too tired to be angry. Lol)