afroewis

public static byte[] FromDateTime(DateTime dateTime)
{
    var daysFirstByte = dateTime.Day / 10;
    var daysSecondByte = dateTime.Day - daysFirstByte * 10;
    byte daysBcd = (byte)((daysFirstByte << 4) | daysSecondByte);

    var monthsBcdFirstByte = dateTime.Month / 10;
    var monthsBcdSecondByte = dateTime.Month - monthsBcdFirstByte * 10;
    byte monthsBcd = (byte)((monthsBcdFirstByte << 4) | monthsBcdSecondByte);