Some folks wonder, what's the big deal? Why figure this out in the first place? I'll tell you one quick reason—it completely undoes a lot of false pictures we have in our minds when we try to visualize these Bible narratives. For another, it can explain what we originally considered inexplicable behavior when we realize how old someone was—or wasn't. You might just want to throw away a lot of those coloring sheets you have used for your Bible classes and maybe create a few of your own.
But the larger lesson for today is this. Just who figured all this out in the first place? Who took the time to find passage after passage, research history, geography, and other assorted minutiae, and then carefully put it all together? Some of it came from scholars whose work was to do just that. But some has come from ordinary people like you and me who simply spend time in the Word, many of whom did so a couple of centuries ago.
They took care of their day to day existence, which meant tilling, planting, and growing everything they ate, preserving the things they would eat during the winter, weaving the cloth to make every item they wore, and carrying water for everything from drinking and cooking, to cleaning and bathing, to watering their considerable livestock, which they also fed and cared for as required, by the way. And they did everything without power equipment or time saving devices. Then they came in worn out at night and by candle or lamplight opened God's Word. They spent so much time in the Word that they could write hymns not based upon one passage, but with each line quoting or alluding to a different passage. Any time something happened in their lives they could quote a scripture that applied. They spent all their "spare" time in that, rather than watching TV, scrolling through Facebook or otherwise surfing the internet, or texting, talking, or simply staring rapt at their phones. That's how those people "had more time than we do." Nonsense.
Some still might think those pieces of information I mentioned above are trivial or even pointless. Seems to me that if God made it possible to figure them out, then just maybe that is exactly what we ought to be doing. As for Jacob's age when he bargained for Rachel, why don't you try that one yourself? Things like that and knowing Jacob's age at the birth of Joseph (that one's easy) might not be essential to my salvation, but spending so much time in the Word of God that I can figure that out too, might just be.
Oh how I love your law! It is my meditation all the day. Your commandment makes me wiser than my enemies, for it is ever with me. I have more understanding than all my teachers, for your testimonies are my meditation (Ps 119:97-99).