YOU SAID:

twas a full moon till the sun came round and the night fell to the morning sun

INTO JAPANESE

太陽が丸くなり、夜が朝の太陽に落ちるまで、満月でした

BACK INTO ENGLISH

It was a full moon until the sun rounded and night fell into the morning sun

INTO JAPANESE

太陽が丸くなり、夜が朝の太陽に落ちるまでは満月でした

BACK INTO ENGLISH

It was a full moon until the sun rounded and night fell into the morning sun