Honestly IT I get all that - I understand it...but here's the problem...
The 6000 years thing is a common belief in Abrahamic circles...
...and the 1000 years is as 1 day to God thing...
...and the seventh day Sabbath (Jubliee/Millennium/thousand year rule of "Christ"...etc.) thing...
and none of this was new in Daniel's day, or in Muhammad's day...
So it is no really great surprise that someone like Daniel (or more likely the "priest" or "scribe" or whoever who used Daniel as a pen name) might have counted back in the genealogical tables and thought to himself - OK - its been about 3700 years now according to the records so there must be about 2300 years left...and then about a thousand years later Muhammad (or someone) comes along and says well its been another thousand years now so there must only be about 1300 (actually 1260) years left now. And then someone gets it down to the exact year 1844 CE - and guess what happens - a man who has deliberately set off to find the "Promised One" whose appearance marks the end of the 6000 years based on these calculations does indeed find someone who seems to fit the bill and sits down and persuades him that he is "the One"...but here's the problem...
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It is very unlikely that someone calculated based Biblical chronologies, and came up exactly with 2300 years, counting from the rebuilt of Jerusalem. The Bible does not give such an easy and exact Chronology, and If you look at the opinions of Scholar, they get the time of Adam a little different from each other, usually their disagreements is about a couple of hundred years.
In the Quran also, it is said 1000 years after revelation of Islam, and then the 5th and/or sixth Imams of Shia, have given hint, it should be counted from the time of disappearance of last Imam. If you think about it, at the time of Revelation of Quran and when sixth Imam was alive, it was unknown that the last Imam would pass away in the year 260AH!
Moreover, you are not even taking into equation many other signs. For example, the Authors of Bible had said, when the End Time comes, the Jews return back to Israel. They had said for 1260 days (years), the Jerusalem will be under the feet of Gentiles. I had shown in some of my other threads, these Prophecies came to pass exactly in the same year (1844). It was also said in both Islamic and Biblical prophecies, after the time of End, all things becomes new. It will be start of a new World. Now, almost all agree that sometime in the 19th century (more or less) a new human era has begun, in the sense that the world is completely changed. A Sudden change! Of course there has always been changes in terms of science or ways of People, but not such a fast change, that all the sudden we see from the 19th century!
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Nothing really happened in 4157 BCE - Siti never had a son in the first place in your illustration and the letters you received were not from Siti at all but from others working on the false assumption that Siti did have a son on the exact day that was indicated, and who sincerely wanted the vision to come true - and they even went so far as to find a German-speaking friend, dress him up in the right clothes and have him "appear" on the street at the right time....
Obviously I used Siti's name just so, it may give you a better feeling about the story. But this Siti I was talking about did have a son, and there was no need for him to lie about having a son, when he did not.
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...and here's the problem...if what I am suggesting was what really happened...how could you possibly know it? Of course I could be wrong - it would be equally difficult to know for sure that the various calculations and letters etc. were not true. But common sense tells me to err on the side of skepticism - otherwise I have to believe every "messiah" that comes along unless I have incontrovertible proof that he is lying.
For me, this problem of yours is not there. Because you are saying otherwise I have to believe every "messiah". I think this is what you are missing: There are many signs given in the previous religions, such as Islam and Christianity with regards to the Promised, so, they may be known. For example in Islamic Traditions it is stated that, the first promised One, whose lineage is from prophet, and his name is alluded to be Ali Muhammad, is the Mahdi who announces from Mecca, then He dies after 7 years. then after Him another Promised One comes, who initially is the follower of the First Promised One, but after His death, this second Promised One is the Spiritual return of Christ, and lives for 40 years. It is written, He will come to Iraq, stays there for 10 years, later comes to the Holy land, and specifically city of Akka,...etc..etc.
Now, you said "otherwise I have to believe every "messiah" that comes along"
The problem with your statement is, firstly the Bab and Bahaullah match the description of every single Prophecy! not just cherry picking. So, here is the challenge:
1. If you think it is easy that any Messiah matches with the Prophecies, just find one out of so many Messiahs and show he matches with 5 prophecies of Islam, or Bible! I am not even asking you find someone who matches all. I let you do you cherry picking!
2. You cannot even find a single prophecy regarding the Promised Ones, that failed to come to pass. and if you become familiar, you would know, their numbers are thousands! So, the challenge is this: find a single Prophecy either from Islam or Bible, and prove it was supposed to be fulfilled in the Promised Ones, abut did not! I let you do cherry picking. Just pick One!
But If you can neither take the first challenge, nor the second, then would you not agree that, it is not " I have to believe every "messiah" that comes along"!
So, that was really the reason I gave the example of the german speaking with 100 signs. It is possible that someone comes having one sign. But the possibility that all signs comes in one person coincidentally is virtually zero or almost impossible, likewise, it is possible that someone from bible chronology calculated that 3700 years passed, 2300 years left. But then you have to say, the Jews starting to return in 1844 is coincidentally happened in the same year, the new era also coincidentally happened around the same time, the person of the Bab luckily had the same name as alluded to, and He coincidentally was killed in the 7th year matching with prophecies, and Bahaullah luckily happened to come to Akka, compatible with prophecies of Islam and Bible, and so on! Now considering that both Bahaullah and the Bab had shown many signs, such as being able to write Books in Arabic very fast and in a style that impressed the scholars. Many testified they could read the mind of them. To say all of it is coincidental and lie, is similar as denying the example i gave regarding the german speaking.