YOU SAID:

Kindest regards of the day

INTO JAPANESE

その日のよろしくお願いします

BACK INTO ENGLISH

I look forward to working with you on that day

INTO JAPANESE

当日もよろしくお願いします

BACK INTO ENGLISH

I look forward to working with you on the day of the event.

INTO JAPANESE

当日はよろしくお願いいたします。

BACK INTO ENGLISH

Thank you for your cooperation on the day.

INTO JAPANESE

当日はご協力ありがとうございました。

BACK INTO ENGLISH

Thank you for your cooperation on the day.