YOU SAID:
My birthday is the day of yester
INTO JAPANESE
私の誕生日はイェスターの日です
BACK INTO ENGLISH
My birthday is Yester Day
INTO JAPANESE
私の誕生日は去年の日です
BACK INTO ENGLISH
My birthday is last year's day
INTO JAPANESE
私の誕生日は昨年の日です
BACK INTO ENGLISH
My birthday is last year's day
That didn't even make that much sense in English.