ANSWER: Each day was 24 hours in length. The account of the recreation (Psalm 104:30) shows that plants were created on the third day of the week. The sun, moon, and stars did not appear until the next day. If these days were a thousand years or more in length as some claim, the plants could not have survived without sunlight.
It should also be noted that although the plants were made on the third day, insects were not created until the sixth day. Plants could not have existed for great periods of time, without the insects. Nor could the insects, such as butterflies and moths, and bees and wasps, survived for long without nectar-bearing plants. Even a basic understanding of nature proves that the days of creation were twenty-four hours in length.
The Bible simply states: “For in six days the LORD made the heavens and the earth, the sea, and all that is in them, and rested the seventh day…” (Exodus 20:11). Each day is exactly what the Scripture says, an “evening and a morning” – that is, a nighttime and a daytime (Genesis 1:5, 8, 13, 19, 23, 31).