What I am asking for is how in the world co they prove astronomically and mathematically when the sabbath was 2000 years ago?

How is this possibe, and what sources did they use?

BTW, this was from an email I receivedThe "Lord of the Sabbath" has the Last Word on the "lunar-sabbath"

The Julian calendar, instituted in 45 B.C.E. by Julius Caesar, is the reckoning of time that is utilized for astronomical calculations and for computing events in ancient history. NASA's calculated accuracy for the Julian calendar is measurably better than 1 millionth of a second. The calculations for the Astronomically and Agriculturally Corrected Biblical Hebrew Calendar for dates before 1582 are all calculated and expressed in the Julian mode. The Gregorian calendar was instituted in 1582 to rectify the miscalculation of leap years inherent in the Julian system. Pontifex Maximus Gregory XIII, added 10 days to the calendar at midnight, Thursday, October 4th, which then became Friday, October 15th. The seven-day week, and the seventh day Sabbath have continued uninterrupted from both the Julian and Hebrew reckoning - and it is highly probable that it has continued uninterrupted since it was begun by the Almighty during creation week (Genesis 1&2).

It has been astronomically and mathematically verified that the Sabbath that Yahshua kept Holy is the same day of the week that it is now. The astronomical proofs are precise to 1/1,000,000th of a second, and the mathematical calculations are accurate to within 1/10,000,000th of a day. This irrefutable data constitutes prima facie evidence that the recently concocted "lunar-sabbath" is pure fiction. If Yahshua did not find it necessary to "renovate" the Sabbath when he was here, but meticulously guarded its sanctity, it is presumptuous and impertinent to assume that someone would know more about the "correct" Sabbath than Yahshua did. I am not of the mind to straighten "the Lord of the Sabbath" out concerning this particular issue! Considering the multiple "fatal errors" in the various lunar-sabbath systems which attempt to invent a sabbath that coincides with the phases of the moon, this is by far, the most fatal. I will stick with Yahshua on the seventh day Sabbath. If he is wrong, I will go to the grave in the same error - just to be safe (Matthew 12:1-8).

Messianic believers can be absolutely confident that they are keeping the same Sabbath that the Creator keeps. Contrary to contrived calculations of the new-age lunar-sabbatalogians and neo-Babylonian solar equinox aficionados, there never has been, and there will never be, a time in which the Sabbath is determined by the phases of the moon or the year discerned by astronomical calculations - no matter how convenient.

One must be able to count to seven to be able to determine the Creator's Sabbath. The second witness and a simple test of basic intelligence that must be met is found in Exodus 34:21 "Six days thou shalt work, but on the seventh day thou shalt rest. . ." thus, one must work six days in order to fulfill the commandment and one must also be able to add 6 + 1 to find the number of days in the Creator's "week" - or in Hebrew, "shevua" a linguistic derivative of "sheva" - seven. The seventh day that we are to rest is the seventh in a series of at least seven. The seventh day comes immediately after the sixth day in the series. It would be more convenient for the Creator to give us a ten-day week since we all have ten fingers to count on. A two-week month consisting of ten days each would enlist the help of our ten toes to culminate the counting. France was once under a ten-day week because their revolution, contrary to America's, was based on secular humansim and they wanted no reliance on, or remembrance of the seven-day week that the Creator gave us. With the seven-day week we must use our intellect to count to a number we don't see on our body - or in the sky. Once we learn to count seven days to find the day of rest, also known as the Sabbath day, we will be familiar enough with the divine pattern so that we can count seven years to find the Sabbath year (Lev 25:4). If we can keep up with the pattern long enough to count seven Sabbath years, we can then enjoy the benefits of the Jubilee - or 50th year. Reinforcing the repeating pattern of sevens each spring, we are commanded to count seven Sabbaths from the Firstfruit Offering to arrive at the day following seven Sabbaths, which is the 50th day - the day that we celebrate the Feast of Sevens, or "weeks" (Lev 23:10-21). Notice how the moon, as from the beginning of creation, has absolutely nothing to do with the counting of sevens? It is mathematically impossible to count the yearly or bi-centennial pattern of sevens accurately by using a lunar-sabbath model. Impossible!

The seven-day week has been used all over the world for thousands of years by many cultures dating thousands of years before the Roman Christian era. Though it is not the only work/rest cycle, it is by far the most common cycle on the planet, and has been so, long before the birth of Yahshua. Jews, who were separated by centuries and continents, were all found, without exception, to have been keeping the same seventh day Sabbath.

With the basic intelligence mankind has been endued with from creation, it appears that, as a general rule, the human race is able to count to seven without losing track. If at one time we did loose track of what day it was, the Creator got the entire nation of Israel back on His calendar before we left Egypt along with their contrived 10-day-week and Babylonian solar equinox calendar. We did a pretty good job of getting the planet on His seven-day week, and many people are actually keeping the seventh day holy. But there is a new wind blowing through the cavernous minds of a sugar shocked generation that looks to the moon for answers that could only be found on a mountaintop in the land of Midian. Moses penned those instructions and we still have them with us to this day. We haven't missed a day of work, or rest, since. Frivolous case dismissed!

Those who have so much time on their hands that they feel compelled to calculate new ways to determine the Sabbath, should perhaps try working 6 days. They will be ready for a rest on the seventh day - regardless of the phases of the moon. . .