During the 20th century, there are at least two examples of when God used dates on the modern Jewish calendar to fulfill His will. 

We are already familiar with the Yom Kippur war in 1973.  On Yom Kippur, a surprise attack on Israel resulted in the defeat of Egypt and Syria.  Israel captured land that included the Golan heights and brought them to within striking range of Damascus. 

Going back a few more years, we find that Purim was reenacted when Hitler's henchmen were hanged following their trials at Nuremberg.  Special newspaper editions on October 16, 1946 reported the execution of ten Nazi war criminals found guilty by the Nuremberg War Crimes Tribunal.

Amazingly, this outcome was hinted at in the Book of Esther!...

"[W]e quoted Nachmanides's assertion (the introduction to his commentary on Genesis) that any change from the usual way of writing a word or letter indicates some hidden meaning.

If we examine the list of Haman's sons, we notice that three letters are written smaller:

the taf of Parshandata

the shin of Parmashta

the zayin of Vizata

(The enlarged vav of Vizata may refer to the sixth millenium.)

The three letters together form taf-shin-zayin, the Jewish year 5707 (1946 C.E.), the year that the ten Nazi criminals were executed.

Of the 23 Nazi war criminals on trial in Nuremberg, 11 were in fact sentenced to execution by hanging. Two hours before the sentence was due to be carried out, Goering committed suicide--so that only 10 descendents of Amalek were hung, thus fulfilling the request of Esther:

"let Haman's ten sons be hanged."

Furthermore, since the trial was conducted by a military tribunal, the sentence handed down should have been death by firing squad, or by electric chair as practiced in the U.S.A. However, the court specifically prescribed hanging, exactly as in Esther's original request:

"let Haman's ten sons be hanged."  The condemned Julius Streicher certainly had no doubts....[as The New York Herald Tribune of October 16, 1946 reported after he ascended to the gallows] "With burning hatred in his eyes, Streicher looked down at the witnesses and shouted: "Purim Fest 1946!"...

If these "coincidences" are not enough, examine the calendar for that month. The date of the execution (October 16, 1946) fell on the Jewish festival of "Hoshana Rabba" (21 Tishrei), which is the day G-d's verdicts are sealed.

This was the very day they were hanged.

Here is my thought.  We spend a lot of time and energy trying to make corrections to the modern Jewish calendar because it may be off by some days, or weeks.  Yet it is truly interesting that God brings about events on the modern calendar that He clearly doesn't want us to miss!

 

Someone (I don't remember who) said that the modern decree for rebuilding Jerusalem went forth in 1968.  This was a bit after the 1967 war which gave Jerusalem back to the Jews.  I would look to see if there was a connection to the month of Nisan when Nehemiah was given the decree to rebuild Jerusalem.
 

I'm guessing that God may be using the days on the modern Jewish calendar to get our attention on the basis of the two events listed above and that there may be other examples too.  I think I read somewhere of other modern calendar parallel fulfillments in the very early twentieth century.  If my hypothesis is correct, this might narrow down our search for likely rapture dates.  I'm looking for answers.  I know the antichrist will seek to change the days for celebration of prescribed holidays, but Hosea (2-11) also says God will change, or stop them. My question is this.  Is God allowing modern fulfillments to take place on days which correspond to the Jewish calendar used in these last days in order that we not miss them?