YOU SAID:
The dog has had a very happy day.
INTO JAPANESE
犬は、非常に幸せな日にきた。
BACK INTO ENGLISH
Dogs have a very happy day.
INTO JAPANESE
犬には、非常に幸せな日があります。
BACK INTO ENGLISH
Dog is a very happy day.
INTO JAPANESE
犬は非常に幸せな日。
BACK INTO ENGLISH
She's a very happy day.
INTO JAPANESE
彼女は非常に幸せな日です。
BACK INTO ENGLISH
She is a very happy day.
INTO JAPANESE
彼女は非常に幸せな日です。
BACK INTO ENGLISH
She is a very happy day.
That didn't even make that much sense in English.