The following is one way to approach estimating the age of the earth, adding and comparing the ages of the patriarchs, reigns of the kings and other dates mentioned in the Old Testament.
1656 years from the sixth day of creation until the flood.
620 years from the flood until Joseph was sold into slavery.
(2276 years from the sixth day of creation until Joseph was sold into slavery.)
430 years sojourn in Egypt.
40 years journey to Canaan.
450 years period of Judges.
40 years reign of Saul.
40 years reign of David.
40 years reign of Solomon.
369 years existence of the Southern Kingdom (Judah).
40 years captivity.
483 years (of Daniel's 70 weeks) till the coming of Christ.
4238 years from Creation to Christ.
Obviously there are variations of interpretation and addition. For example, when do the 430 years of affliction start? If started with Abraham instead of Joseph then approximately 4048 years from Creation to Christ.
[Note: I got the period of Judges by adding the servitude years plus the years of rest. Some students believe there could be some overlap in the different judges' years. I got the years of Southern Kingdom by adding the reigns of the kings, but also cross-referencing them against their reigns compared to the reigns of the Northern kings. And then there is when the 70 weeks hit in reference to Christ -- his birth? triumphal entry? etc.]