YOU SAID:
We went to London in the eastern holidays
INTO JAPANESE
私たちは東部の休暇にロンドンに行きました
BACK INTO ENGLISH
We went to London on our eastern vacation
INTO JAPANESE
私たちは東部休暇でロンドンに行きました
BACK INTO ENGLISH
We went to London on our eastern vacation
That didn't even make that much sense in English.