Take a step back for a few moments and try and consider this situation from a few different angles.
For the sake of discussion, my comments will be centered around the idea that this not a technical glitch of some kind, and Apple knowing removed the two dates.
1) Whether you or anyone else agrees with what has transpired, we (as believers) are still free to recognize the two dates, and to worship as each of us sees fit. The removal of the acknowledgment of the dates from the calendar does not really change anything with any person's personal faith.
2) In my opinion, there is no real reason to be sad. Apple, as a corporation, is made up of and managed by many different cultures and beliefs. As such, there are going to be times when Apple does something (major or minor with policy or execution) that we may not agree with. So long as the subject of the disagreement does not infringe on anyone's Constitutional rights, or violate local, county, state or federal laws in a way that affects us, (the consumer) Apple is free to make decisions and policies that I may not agree with.
When the aforementioned occurs, I stop and ask myself is the disagreement some kind of violation? If it isn't, I then ask myself is my disagreement based on conviction or preference. If the former, is my conviction rooted in something more than feelings? If the latter, is it really worth giving the action a second thought?
Remove the emotion from the equation, and there is no real cause for sadness or anger (depending on the person) with Apple.
To me, this isn't even a blip on the radar.