Some words about date-finding using Biblical chronology;
As Stephen pointed out, the number of years from the birth of
Cain (or maybe Seth) to Solomon can be calculated directly. As
for the most significant dates thereafter, I don't think it
matters all that much; most of them (e.g. Babylonian captivity,
destruction of Jerusalem, etc.) are known within a few years from
secular history, archaeology, etc. Using these dates to date the
earth requires the literal interpretation of the creation account
and 6 actual days of creation.
Why must the birth of Christ be calculatable from the Old
Testament? Unless you do not believe that Jesus of Nazareth was
the Messiah you can find what you need in the New Testament
combined with secular history. However there is one OT clue that
I can't remember the reference. It has to do with Rachel crying
for her children in Bethlehem and Ramah "because they are not".
This is usually interpreted as the slaughter of male children 2
years old and younger in the area around Bethlehem. This was
ordered by Herod the Great, the vassal king over Judaea. The Wise
Men came looking for "the King of the Jews" and Herod told them
to come back and tell him where this King was so that Herod could
then go and worship, too. Some say that this occured 2 years
after the actual birth of Christ but this is preposterous. This
king Herod was extremely suspicious and paranoid even to the
point of executing some of his own sons whom he percieved to be a
threat. The Roman Emporer Augustus was reputed to have said in
reference to this "I'd rather be Herod's hog than his son"
because a hog would not be killed and eaten due to the Jewish
dietary rules. Reports of angels heralding the birth of a new
king would have undoubtably reached Herod through his informants
within a few days of the event. The reason that he killed all
those 2 years and younger is that he wanted to be sure he wasn't
taking any chances. In all likelihood the Wise Men showed up on
the night of Jesus' birth, leaving their expensive gifts, which
Joseph was able to use to use to finance the flight to Egypt,
which he had been instructed in a dream to make. The NT also
states that Jesus and his parents were also able to return in
time for him to be dedicated in the tmeple when he was 40 days
old (as required by OT law) because Herod the Great had died. The
date of this Herod's death is also known within a few years from
secular history.
One more parting shot, I'll repeat an argument I got from a Bible
teacher I respect. If you don't believe Jesus of Nazareth was the
Messiah and you are still waiting: How will the Messiah prove his
lineage to David if and when he does finally show up? At the time
of the NT, these records were kept in the temple and it was
common knowledge even to those who did not believe in Jesus'
diety that he was the descendant of King David, heir to the royal
throne. These records were destroyed along with the temple and
much of Jerusalem by the Roman General Titus in 70 AD. Has any
one else been keeping a credible record of the Jewish royal line?
If not, the Messiah had to come before 70 AD.