It is generally accepted that Abraham lived 175 years. However, the dates when he lived are rather fuzzy and hotly debated.
When was he alive and what reasons would you give for your conclusion?
What methods have gone into determining the dates in which Abraham (and perhaps other early biblical figures) lived and died?
The best way to find this estimate is to take known historical dates and work backwards from there using dates and durations in the Bible.
The Mesha Stele has been dated to about 840-850 BCE, and seems to pretty clearly describe the time of Omri. If we assume it was written when the events happened, not long afterwards, we can use it to work backwards. Omri's reign began in the 31st year of Asa and lasted twelve years, which means that Asa's reign began around 870-890. Previously, Rehoboam ruled for 17 and Abijah for three. Although the transition is not entirely clear to me, the prior ruler was apparently Solomon for 40 years. In his fourth year, he started to build the temple, which was 480 years after leaving Egypt. So that takes us back 20+36+480 = 536 years further, to 1406-1426 BCE as the dates for the exodus.
Now we come to a difficult stretch because there are, to my knowledge, no clear chronological links between Moses and, say, Joseph. Moses' grandfather Kehat was with Jacob on the way into Egypt, and if you add up all the ages that's a maximum of 350 years (actually surely less, since Kehat was not an infant), but it's not clear what the minimum was. The most direct statement is Genesis 15:13, which puts four hundred years between Abraham's offspring and the exodus. Since the phrase is "in a land that is not theirs", and Ishmael and Isaac did not start off owning the land, it seems that the most harmonious interpretation is that this was 400 years from Ishmael's birth. We find that Abraham was 86 years old at the time. The 400 years probably didn't end until after wandering in the wilderness for 40 years, so that's 360 years from Ishmael's birth to the exodus.
Therefore, according to historical and Biblical evidence, Abraham was born somewhere in the range of 1852-1872 BCE and died 175 years later (1677-1697). If the 400 years are accounted for differently, these dates could change significantly.
For what it's worth, other people have studied the matter and come up with different timelines; it's complicated by the lack of accurately-dated historical evidence for events prior to David upon which to anchor the timeline.
(Beware of lots of little edits to fix up small mathematical errors and other details.)
Answering this question over 10 years after it was posted gives both an advantage and a disadvantage. The disadvantage is that the preferred answer has been chosen, which my answer disagrees with. The advantage is that the various arguments and calculations can be compared and that it is worth-while posting another one which agrees with the 2166 to 1991 B.C. era answers, as it presents a slightly different route.
This route is the "working backwards" one (which is something I am strangely prone to do a lot, myself). I quote now from the booklet below, re. how to find a starting point in developing a biblical chronology:
"One of the problems faced in this pursuit is that the biblical chronological data is all relative rather than fixed. In other words reference points are taken from elsewhere in the historical narrative. This means that, in order to make a start, you have to identify a fixed, objective and external time reference from which to calculate all other dates. There are in fact two such fixed, external points that we can work from.
1 - 586 BC - It would appear that there is virtually universal agreement, both among biblical and non-biblical scholars, that the fall and destruction of Jerusalem occurred in 586 BC.
2 - 931 BC - Again, there is widespread, though certainly not universal, agreement that the division of the kingdom following the death of Solomon happened in 931 BC.
...Starting from these fixed reference points and working backwards, it is possible to determine with a real degree of certainty, other dates in biblical history, alll the way back to Abraham...
the kingdom was divided in 931 BC, after Solomon's death
since Solomon reigned for 40 years (1 Kings 11:42), he must have become king about 971 BC
Solomon began building the temple during his fourth year as king (1 Kings 6:1), i.e. c.966/7 BC
at the time of the Exodus, Israel had been in Egypt for 430 years (Exodus 12:40), so Jacob must have gone to Egypt in 1876 BC
Jacob states that he was 130 years old when he appeared before Pharaoh (Genesis 47:9), so his birth can be dated at about 2006 BC
Isaac was 60 when Jacob was born (Genesis 25:26), so his birth would have been about 2066 BC
Isaac was born when Abraham was 100 (Genesis 21:5), so Abraham must have been born in 2166 BC." A Concise Chronology of the Bible, p10, John D Brand, Edinburgh Bible College 2014
According to the Bible, Abraham was born 2166 BC, and died 1991 BC, starting from well-established dates.
The reign of King Solomon began 971 BC. (See "Mysterious numbers of the Hebrew Kings" by Edwin Thiele.)
(You could also use 587 BC for destruction of Jerusalem by Babylonians, and the year of Ezekiel 40:1 (14th after destruction of city), together with Leviticus 25:9-10, and the Seder Olam's information that the Jubilee Year in Ezekiel 40:1 was the 17th Jubilee (with Jubilees happening every 49 years, plus 40 years in the wilderness, to get 1446 BC for the year of the Exodus. See answer to "When was David born?" for an explanation of this route.)
1 Kings 6:1 :- 971 BC - 4 = 967 BC, Solomon’s Temple began to be built
1 Kings 6:1 :- 967 + 479 = 1446 BC, Exodus
Exodus 12:40,41 :- 1446 BC + 430 = 1876 BC, Jacob enters Egypt at Passover after two failed harvests, before the third failed harvest, early 3rd year of famine in days of Joseph.
Genesis 47:9 :- 1876 BC + 130 = 2006 BC, Jacob born
Genesis 25:26 :- 2006 + 60 = 2066 BC, Isaac born
Genesis 21:5 :- 2066 + 100 = 2166 BC Abraham born
Genesis 25:7 :- 2166 – 175 = 1991 BC Abraham went to glory.
So Abraham was born 2166 BC, and died 1991 BC.
I, along with others, have done studies on the chronology of the Old Testament genealogies - which puts Abraham being born ~1950 years after Adam, and about 300 years after the flood.
Given that the earth is approximately 6000 years old, that makes Abraham's birth about 2050BC.
Dating biblical events from Creation and/or from the Christian Era depends on the positions adopted on two disputed points:
Early birth: Terah was 70 y.o. at Abraham's birth and therefore 145 y.o. at Abraham's departure from Haran.
Late birth: Terah was 130 y.o. at Abraham's birth and died being 205 y.o. before Abraham's departure from Haran.
The position on this point affects the date from Creation of biblical events from Abraham's birth forward, and the date from the Christian Era of biblical events previous to Abraham's birth.
Short sojourn: 215 years.
Long sojourn: 430 years.
The position on this point affects the date from Creation of biblical events following Jacob's entry into Egypt, and the date from the Christian Era of biblical events previous to the Exodus.
Thus, each of the 4 possible combinations of the positions on these disputed points can give a different date for a biblical event, either from Creation, or from the Christian Era, or from both.
In the particular case of Abraham's birth:
the date from Creation (AM, Anno Mundi) depends on the position on his birth; and
the date from the Christian Era (BC, Before Christ) depends on the position on the sojourn in Egypt.
IMHO, a good source for an introduction to the two disputed points and links to further bibliography is:
https://creationwiki.org/Biblical_chronology_dispute
From that source I made the following table with the year of Abraham's birth in the format (AM, BC) for each combination of the positions on the disputed points, adding 1 to the BC dates in Thiele's chronologies because in each system the sum of the AM and BC dates of any event, including Creation, must be constant:
| short sojourn | long sojourn |
------------+---------------+--------------+
Early birth | (1948, 1952) | (1948, 2167) |
------------+---------------+--------------+
Late birth | (2008, 1952) | (2008, 2167) |
------------+-------------- +--------------+
Note on the short sojourn position
The short sojourn position fits a literal reading of Moses' genealogy from Levi (Ex 6:16-20), noting that Levi's son Kohath had already been born when Jacob entered Egypt (Gen 46:11). Denoting Kohath's age at the entry into Egypt as K_E, Kohath's fathering age (i.e. his age at Amram's birth) as K_FA and Amram's fathering age as A_FA, and since Moses was 80 y.o. at the time of Exodus (Ex 7:7), we have:
Exodus - Entry into Egypt = K_FA - K_E + A_FA + 80
where Kohath's and Amram's begetting ages must be less than their respective lifetimes and K_E must be greater than zero. Thus, a sojourn time of 215 years can be achieved in a number of ways, such as setting the fathering ages at the middle of the respective lifetimes:
For K_E = 1, K_FA = 67 & A_FA = 69, sojourn time = 215 years
This is fully compatible with Num 3:27-28 stating that the number of male descendants of Kohath was 8600, as e.g. in this way:
Years - Age --- Age ----- Age -- Age -- Kohath's
from -- of ---- of ------ of --- of --- patrilineal
entry - Kohath Jochebed Amram Moses male descendants
0 --- 1 --- .. ---- .. --- .. --- .
30 --- 31 --- .. ---- .. --- .. --- 4
60 --- 61 --- 15 ---- .. --- .. --- 4 x 4 = 16
90 --- 91 --- 45 ---- 24 --- .. --- 16 x 4 = 64
120 --- 121 --- 75 ---- 54 --- .. --- 64 x 4 = 256
150 --- xxx --- 105 ---- 84 --- 15 --- 256 x 4 = 1024
180 --- xxx --- xxx ---- 114 --- 45 --- 1024 x 4 = 4096
210 --- xxx --- xxx ---- xxx --- 75 --- 4096 x 2 = 8192
