Unfortunately, doesn't really hold up. Reading the whole passage, you see things like Gen 5:9:
"And Enos lived ninety years, and begat Cainan"
If we're still talking lunar months, that means Enos became a father aged seven and a half.
For Methusalah's age to be given in months, rather than years, you would need to explain why there is a jumping from one style of measurement to another (and back, several times over) in the same passage.
Better explanation? It was all just made up, yer honor.
Sure, all the supernatural stuff was made up for obvious reasons, but why would they have made up people's ages?
Oral tradition is enough to account for the different measurements throughout the bible and other contradictions such as different versions of the same story. But here, the bar mitzvah marking the beginning of adulthood makes sense (ty Samothec).
In addition to what graybeard and others said, we are talking about hebrew, a language that is still in use. And the people who use it regard a year as a specific thing which is distinct from a lunar month. In fact, they define a year by a fixed number of lunar months. That the age of methuselah works out when divided by 13 is coincidental and does not make your case, given the number of other ages that do not work out so well.
I understand that language and word usage changes over time. but for jews, tradition is of utmost importance. obviously, since many of them still use their antiquated lunar calendar. So I find it unlikely that over time the word for year at one point actually meant month.
So what's your explanation? They actually lived hundreds of years? I actually think you make my case here, since they base their calendar around lunar months. It would be quite easy to make the leap to a person's age as the total number of lunar months. It would be like bragging for the really old. I can see it now:
Grandson: How old are you, grandfather?
Grandfather: Very old, grandson.
Grandson: But how old? When were you born?
Grandfather: Many moons ago, grandson...
I think someone struggled to find some possible interpretation so the Bible doesn't look stupid.
LOL that's going to be pretty difficult. Unfortunately, the original writers aren't around, so we have to come up with ideas as to what they were really saying.
"I have a badger's hole filled with pens." because "set" also means "a badger's den or hole."
Of course, because people sometimes fill badger's holes with pens. I can see that. In fact, it makes more sense than having a set of pens. Who would have a set of pens? Crazy people, that's who!
On top of that, you think that God is unable to express himself properly.
YHWH isn't quoted in Gen 5. Also, if he put a limit on people's lives, why did they live longer than that? Are you assuming that everything in the bible should be taken at face value? No errors? All the supernatural stuff is true? Because that's how you come off, like the contradictions make sense in your mind. This is all very confusing to me.