YOU SAID:
it will be my birthday next year
INTO JAPANESE
来年は私の誕生日になるだろう
BACK INTO ENGLISH
It'll be my birthday next year.
INTO JAPANESE
来年は私の誕生日になります。
BACK INTO ENGLISH
Next year will be my birthday.
INTO JAPANESE
来年は私の誕生日になります。
BACK INTO ENGLISH
Next year will be my birthday.
That didn't even make that much sense in English.