Imitation of the Kuffaar

​Shaykh Saalih al-Fawzaan said: 
The things in which the kuffaar are imitated include acts of worship, such as imitating them in matters of shirk, such as building (structures) over graves, building shrines and exaggerating about them. The Prophet (peace and blessings of Allaah be upon him) said: “May the curse of Allaah be upon the Jews and the Christians, for they took the graves of their Prophets as places of worship.” Al-Bukhaari, 425; Muslim, 531. And he told us that when a righteous man among them died, they would build a place of worship over his grave, and install images therein, and that they were the most evil of mankind. Al-Bukhaari, 417; Muslim, 528. Nowadays there are instances of major shirk because of exaggeration concerning graves, as is well known to scholars and ordinary folk alike. The cause of that is imitation of the Jews and Christians. 
Another example is their imitation of the festivals of shirk and bid’ah, such as birthday celebrations, whether it is the birthday of the Prophet (peace and blessings of Allaah be upon him) or the birthdays of presidents and kings. Or these festivals of bid’ah and shirk may be named after days or weeks, such as a country’s national day or independence day, or Mother’s Day, or hygiene week, and other days or weeks that are celebrated. All of these have come to the Muslims from the kuffaar, for Islam has only two festivals: Eid al-Fitr and Eid al-Adha. Anything else is bid’ah and an imitation of the kuffaar. 
From a khutbah entitled al-Hathth ‘ala Mukhaalafat al-Kuffaar (Exhortation to be distinct from the kuffaar) 
Ref: https://islamqa.info/en/45200