Of course, the way most cultures interfaced with each other in the ancient world, was in war. Unfortunately, in antiquity, the losers of wars were not permitted to write histories. This has resulted in huge gaps in man's written record.

Further challenging the accuracy of the world's chronology is the fact that some leaders (even leaders from the same culture) hated their predecessor, and attempted to have all references to them removed from the written record. Some of these efforts are known. For instance, in the ancient Assyrian records called "Eponyms," it is well known by comparing the Assyrian history with the Babylonian history, that early Assyrian historians completely expunged all the times when Assyria was under foreign rule, out of their records.  The Babylonian histories have made us to understand that there were gaps of which we would otherwise have no knowledge.  No one can comment as to whether or not other such gaps exist.  

Man's written record of the chronology of the world develops a very good rate of accuracy about 320 BC, when the empire of Alexander the Great had been split four ways to his four generals. These were all of Greek culture. They all used the same calendar.  They all kept written records, and they interfaced with each other in ways other than war, making political marriages and military alliances with each other.

Before that time, man's record is entirely suspect, and generally is supplied by the guesses of archeologists. For instance, prior to the 1990s, it was generally understood that the first Babylonian invasion into Israel occurred in 612 BC. With modern archeological techniques, this has been changed to 604 BC. These kinds of wide swings are not uncommon when dealing with the world's history before the Greek Empire.

Indeed, when dealing with antiquity, the world's teacher have two mainstream chronological thoughts that are as much as ten years from each other, as recently as 460 BC. The farther back into antiquity we go, the wider the gap becomes. There is yet a third line of thought developing, called the "New Chronologists" who suggest that the ancient dates are off 250 or more years.

The reason for the great gap between the New Chronologists and the mainstream teachers is a period called by the mainstream group "History's Dark Ages" from 1200 BC to 800 BC. There is very little archeological data from this age. They infer this time line, due to other archeological data they have. The "New Chronologists" deny the existence of this period being 400 years, and shorten the time greatly, depending upon the teacher.

Most of the chronologists and archeologists that are well respected by the world, believe their dates are now fairly good back as far as 640 BC. After that, they will readily agree to swings of 30 years back to 900 BC, and 300 year swings after that.

But archeologists admit that even those dates are very pooly established. For instance, the common denominator for the dates of the 700s to 1000s BC is an eclipse of the sun in the 9th year of an Assyrian King named Assur-Dan. This eclipse is recorded in the Eponyms of Assyria, a document which is thought to give an annual account of the events of Assyria for a continuous period of 261 years. Now eclipses occur with mathematical precision, and it can be determined astronomically when they have occurred in the past. By finding the date of this eclipse, it is thought that a firm date can be established to "anchor" the Assyrian list of Kings to a specific date in history, along with other events recorded in the Eponym (notably, the war between Assyria and Ahab, and the collecting of taxes from Jehu, 14 years later) which is what has been done.

The generally accepted date for this eclipse is 763 BC. There was a total eclipse of the sun in Nineveh at that date. But there were other eclipses as well. For instance, there were eclipses which would have been visible in Nineveh in 723, 751, 791, and 809 BC.

The eclipse dated at 763 would agree with the history of Israel and the fall of the 10 tribe kingdom to Assyria around 718 BC. However, it disagrees by about 55 years with the reign of Ahab and Jehu. If the eclipse is determined to be the one in 809 BC, then the dates of Ahab and Jehu agree with the Scriptures, but the dates for the fall of Israel differ by the same 55 years.

The "New Chronologists" argue that the Assyrian Eponyms, generally thought to be consecutive years by the mainstream chonologists, are not complete. They point out that the more ancient Assyrian Eponyms (such as those dated around 1400 BC) are known to have gaps such as we previously alluded, which exclude all the years in which Assyria had been conquered by a foreign power. The Babylonian archeological finds indicate years in which Nineveh was subject to Babylon, but the 1400 BC Assyrian Eponym list either never included Bablonian rulers when they dominated Nineveh, or if included, later expunged them from the Assyrian lists. That this happened is agreed to by all archeologists/chronologists.

The New Chronologists point out that there were many years in which Assyria would have been a very weak power in the 700's BC, in which Assyria would have been liable to have been conquered by a neighboring power. The New Chronologists argue this has taken place, though there is no direct archeological evidence of it ever occurring. The New Chrologists argue that some years for Nineveh being laid to tribute must be added to the list, and that the Assyrian Eponym list cannot be considered to be complete or chronological.

Mainstream chronologists mock this idea, but have not been able to show conclusively that it is wrong. In fact, very little discussion on it has taken place. Most of the efforts to fight with one another deal with shortening the chronology back in the 2000 BC era, and the chronology of Egyptian Pharoahs, and are less focused on the extending of dates in the 700 BC era.

It appears to me that both sides have some answers, according to the chronology given by the Bible. For instance, mainstream chonologists start the organized Egyptian line of kings before the Bible date for the flood. The flood, by Bible Time occurred in 2246 BC. The New Chronologists place the first Egyptian dynasty in the 2200s, quite consistent with the flood. The mainstream places it some 300 years ealrier. On the other hand, the New Chronologists deny that the Egyptian Pharaoh Shoshonk I was King Shishak who invaded Israel in the 4th of Rehoboam. The evidence seems strong that he was, only as King, not as Pharaoh as alleged by the mainstream group, and therefore at a slighly earlier date then they allow. But as I said, for the consideration of this chronology, we will not pay any attention to the dates of either school, except for pointing out relevant coincidences. All our dates will be according to the Scriptural record, rather than the dates given by man. My dates are generally about 100 years off of the main stream of thought for the date of creation. By the Exodus, they are about 60 years off. And by the end of the kings, they are falling 1 -3 years off of Man's records. Following the start of the Persian reign, they fall between two lines of main stream thought.

After we get into the more reliable periods of man's history, my chronology happens to fall between the two lines of mainstream thought.

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Just to make sure it isn't ever easy, there also exists no year "0" in the archaeological dating systems.  Unlike our modern birthday keeping, the first year, or year one, is the first year of someone's life, not the completion of that year.  So if an event occurred in 1 BC, and lasted to 1 AD, this is only 1 year, though if one tried to do the math, +1 - (-1) = 2.  In  archaeology, however, it is only 1.  When crossing the O year, this must always be adjusted for.

Some individuals (usually scientists considering astronomy) use what is being called "astronomical time."  These dates are shown as negative numbers, and do include the year "0."  So as a general rule, when you see the date expressed as 604 BC, or 604 BCE, this system does not include the year "0."  But if you see the year expressed as simply -200, then it does include the year "0."

Lets use, for an example, the punishment of Israel which God promised them through their law (Lev. 17.)  Moses said Israel would be punishes seven times for their sins.    The seven times is 360 x 7 or 2,520 years.  The date for the start of this punishment, which was of course the invasion of Babylon (the head of Nebuchadnezzar's image,) would be 2520 years earlier from the year in which Israel was freed from rule by some element of Daniel's image.  That punishment ended in 1917 AD, when Israel was finally freed from captivity to the nations of Nebuchadnezzar's image (Turkey, at that time.) 

1917-2520=603+1 or 604 BC. 

Likewise, if we were to figure the matter backwards, it would be:
604 BC + 2520 years = (-604) + 2520 years = 1916 + 1 = 1917. 

But if we were to ask, how many years are there between 604 BC and 1917 AD, the answer would be"
1917 + 604 = 2521 -1 or 2520 years. 

So if you are adding or subtracting dates across the year "0," you must add a year. 
If you are calculating the amount of years between dates, one AD and the other BC, you must subtract a year.

Astronomical time requires no such adjustment.  It works just like mathematics.