YOU SAID:

It's their anniversary on Monday. They shall be married for 15 years, I think.

INTO JAPANESE

月曜日は彼らの記念日です。彼らは15年間結婚するだろうと私は思います。

BACK INTO ENGLISH

Monday is their anniversary. I think they will get married for 15 years.

INTO JAPANESE

月曜日は彼らの記念日です。彼らは15年間結婚すると思います。

BACK INTO ENGLISH

Monday is their anniversary. I think they will get married for 15 years.