The Logos Blog recently posted an article regarding "Jewish Feast Dates" and whether those date can be ascertained in Logos. The article said "yes" and listed the procedure.
Technically, the article is correct...and technically, it is incorrect. If a person is in fact looking specifically for "Jewish" Feast Dates, the method described will provide that info.
However, if a person is actually interested in BIBLICAL Feast Dates, then the answer is simply "no"...Logos has no method for providing those. The reason is because the Jews instituted a non-Biblical method for identifying the Biblical moh`:adhiym (appointed times), including the hhaghgiym (feasts), basing their dates on calculation of the conjunction rather than on the Biblical observance of...observance.
The calculated dates of conjunction can be rendered centuries and millennia into the future (thus the dates listed in the Logos Interactive Media Tool). However, the Bible clearly states that things are confirmed by two or more witnesses, and this method of confirmation (witness) was applied to declaring new months as well.
Both Josephus and Philo state that months, and therefore the year as well, begin with the observation of the first crescent. The Jews deliberately altered their methodology after the Romans expelled them from the land and the normal process of declaring months by observation was deemed impracticable. The Rabbi Hillel II imposed the calculated 19-year intercalated calendar in the mid-4th century, but the calendar as currently followed didn't come to full implementation until centuries later. One of the current attributes of the current Rabbinic calendar is the presence of postponements, which by Rabbinic decree are inserted into the calendar to specifically assure that there are never two consecutive Sabbaths for two days in a row. In other words, the fifteenth day of the first month, which is one of the seven yearly Sabbaths, is never allowed to fall on the day before or the day after the weekly Sabbath. This is an unbiblical ruling of the "Corban" variety.
One of the factors that causes the variance of the two calendrical systems is that the Rabbinic one begins on the date of conjunction (the point when the moon is closest to the sun) and the Biblical one on the evening of the visible crescent, dates which are always at least one day's variance. Another factor that can cause confusion is that astronomers have used the term "new moon" to describe the invisible conjunction, which is the same term the Bible uses to describe the first visible crescent. To be clear, conjunction is actually "no moon", not a new moon.
Another factor that introduces a lot of confusion is that Jews almost universally declare Passover as falling on the 15th day, when Lev. 23:5 plainly and explicitly declares Passover as occurring on the 14th day. There are narratological and prophetic reasons why Jews have imposed this error on their calendar, but I won't cover that here. The primary point I'm making here is that for those wishing to properly observe YHWH's prophetically declarative moh`eidhiym and hhaghgiym, the dates in the Logos Interactive are not satisfactory.
A website that provides accurate and dependable dates is renewedmoon.com. I have had some difficulty getting the website to load properly on many occasions (that is, the most important info--the dates--don't load into the browser), but they have a link to their mobile app near the top of the screen that does fully load the current dates.
EDIT: here is the mobile site...http://www.renewedmoon.com/mobile-site/renewed-moon-report.htm
