Brahmaa, the Creator, creates the world and everything there-in. Brahmaa is not human, though. Due to thier own (human)-limitations, Humans conclude that they are the highest form of creation. This is ture with all the Gods (I am using plural of the supreme God, out of necessity).

The Creator and His creation appear simultaneously on the scene, as there can be no creation without a creator and no one can be a creator without creating something.

Our World consists of the relatively longer-lasting Earth (the 'elements') and all the Other Things that populate the earth (like humans, animals, plants etc.), which are short-lived and hence keep changing. Lord Brahmaa is the Creator. Brahmaa 'appears' when the earth appears (is created) and He 'disappears' when the earth disappears (disintegrates).
So the life-span of the earth is the same as that of its Brahmaa.

Brahmaa's Life
Brahmaa has His own day, His own month and His own year. A Brahmaa's total time is 100 Brahmaa years; 1 Brahmaa year is 360 Brahmaa days.

Each day of Brahmaa consists of 1 Brahmaa's day-time and 1 Brahmaa's night. One day-time = one night = 4,320,000,000 human years (4.32 Billion years). Note 432 is easy to remember as these are decreasing digits. People familiar with Hindu poojas may be aware that 1 ashtothram is 108 Naamaavali and 4 x 108 is also 432!

Brahmaa's Brahmaa's Humans'
1 Day-time   4,320,000,000 years
1 Night-time   4,320,000,000 years
1 (Full) Day Day + Night 8,640,000,000 years
1 year 360 Days 3,110,400,000,000 years
Brahmaa's Life 100 Brahmaa's Years31,10,40,00,00,00,000 Human years
Brahmaa's Life 100 Brahmaa's Years311,040,000,000,000 Human years

One Brahmaa, One Earth & 36000 Worlds
Brahmaa is active with the creation during the day-time and 'sleeps' (rests) during His night. When the creation starts, Brahmaa creates the 'World' by first creating the Earth and continuing to populate it by creating and re-creating the various 'things'.

At the end of a day-time of Brahmaa, heat increases enormously (sun becomes seven times intense) and this is followed by heavy rains submerging the entire earth making it un-inhabitable. In other words, the World 'ends' but not the Earth. This remains so, for the entire night-time of Brahmaa. This repeats every day for all 36,000 days of Brahmaa. So the Earth remains for the entire life of Brahmaa but the World is re-created 36000 times.