As a divinely inspired document the Bible is in its totality the word of God, but it was not composed by a single human author, at a single sitting, but rather collected over eons from the inspired writings of man.
The Old Testament is considered by biblical scholars to be collections of books from both the northern Kingdom of Israel and the southern Kingdom of Judah. Knowing this it is not so unusual that God might be referred to by different names in books written in either the north or south.
The name of God that appears most often in the bible is the Tetragrammaton, that is the word with four letters יהוה translated as YHWH or more commonly seen as Yahweh. A modern corruption of this is Jehovah.
Another name that appears quite often is Elohim, which is related to the concept of divinity and divine power. Elohim is not used uniquely for God, but also is used to refer to other gods, such as "You shall have no other gods before me."
Now the Israelites did not say the name of God. Indeed YHWH contains no vowels, and so is technically unpronounceable, so when reading Scripture aloud the reader would instead say "Lord", that is Adonai.
Modern Christians have different names for God. He is called the Three-In-One, The Father, Son and Holy Ghost, Deus which is Latin for Lord. Abba is how Jesus himself referred to God. It means quite aptly "Father." Jesus himself is often called by many names. Iesus, Joshua (which is the same a Jesus), the Lamb of God. The Way, the Truth and the Light. The Living Water. The Vine. The Apostles called him Rabbi, which is teacher, and Master.
The Holy Father has said the most appropriate name for God is אהיה אשר אהיה that is ehyeh-asher-ehyeh or in English "I AM that I AM." That is because it encompasses the concept of the eternalness of God.
There's an old joke told by and about St. Augustine. A man walks up to St. Augustine and asks "What did God do before he created the World?" Augustine answered, "Nothing, He didn't have the time."
Okay, Okay. Geek joke.
But what the philosopher meant was that before the world existed there was no time. Modern physicists recognize this as a scientific concept. In order for time to exist space must exists. The two are linked. If there is no space there is no time. So when God created the Heavens and the Earth he also created time. So in a real sense God existed before there was existence, before there was time. So he is not bound by time.
This opens up all kinds of interesting concepts.
We pray to God to ask for something for tomorrow and to thanks him for yesterday. But we can just as validly pray to ask for something in the past. This is most commonly done when we do not know the outcome of something, say the state of a soul at death and its disposition in the afterlife.
Since God is not bound by time, yesterday, today and tomorrow are all the same to him. Easy to see why and how he would know the future. It is the same to God as the past. And since the way we mark time is by the changes that occur, the moving of a hand, the growth of a tree, if God is unbound by time he will never change.
So HE IS, always. He will be as unchanged at the end of the world as he was at its beginning, and beyond. For though we know that there was no time before existence began, was also believe that there will be a time after the end of the world, where we will live in a new Heaven and a new Earth for eternity. So time, now that it exists will go on forever to the future, a future during which God will always exist.