Are there some days that God hates? Should we celebrate holidays in church?

My initial answer would be that God does not hate any day. Psalm 90:14O satisfy us early with thy mercy; that we may rejoice and be glad all our days.
See All... states, "O satisfy us early with thy mercy; that we may rejoice and be glad all our days." The believer is allowed to be glad on every day.

However, trying to read deeper into your question, I believe that you are referring to our celebration of special days, such as holidays, birthdays, and anniversaries. I would have to say that God does not want us celebrating everything that man finds a reason to celebrate. That does not mean that God hates the day, but He may hate the thing being celebrated. I doubt that God appreciates the celebration of Earth Day or of Gay Pride Day. But this is true in many things. Humans are often celebrating things that God would not celebrate. Again, God does not hate the day, but only the meaning that some have placed on the day.

This of course brings up the holidays and the question as to whether or not Christians should participate in them. Some of this is based on personal conviction. In fact, God does not tell us what to do in every case. Consider this passage:

Romans 14:5-6 [5] One man esteemeth one day above another: another esteemeth every day alike. Let every man be fully persuaded in his own mind. [6] He that regardeth the day, regardeth it unto the Lord; and he that regardeth not the day, to the Lord he doth not regard it. He that eateth, eateth to the Lord, for he giveth God thanks; and he that eateth not, to the Lord he eateth not, and giveth God thanks.
See All... One man esteemeth one day above another: another esteemeth every day alike. Let every man be fully persuaded in his own mind. He that regardeth the day, regardeth it unto the Lord; and he that regardeth not the day, to the Lord he doth not regard it. He that eateth, eateth to the Lord, for he giveth God thanks; and he that eateth not, to the Lord he eateth not, and giveth God thanks.

God allows us to respond to many holidays according to our personal convictions. However, that does not mean that pagan practices of the holidays do not need to be pointed out by Christians. Personally, I see so much evil in the celebration of Halloween that I cannot have any part in it. To me, Christmas is mixed. There are parts of it that I can have no part in, but there are other things that I enjoy with clear conscience. I do not bring the secular elements of Christmas into our church. It is a place of sacred worship and we need to guard its purpose. Yet, I am glad to remind people of the precious coming of Christ during this season. We need to be a witness to the world during this time.

You also ask about birthday and anniversary celebrations. I do not know of any biblical statements concerning this practice. These celebrations seem to be a part of our modern world and culture. Unless they somehow disobey a biblical teaching, they would be allowed. I see no problem with them.