I say, and with God's success: It is permissible to congratulate them on the holiday before the holiday, and it is not considered an innovation if one says: May you be well every year, rather it is part of the good connection and communication among Muslims. It is permissible at any time before and after the holiday. Those who are strict about such matters should be feared, as they seek to create doubt in people's lives and to sever connections between them, and this is the true innovation in religion. And God knows best.