It is no coincidence that Rosh HaShonnoh, Yom Kippur, Sukkos, HoSha’ano Rabo, Sh’mini Atseres and Simchas Torah are placed in juxtaposition. There is a supernal process going on that starts with Rosh HaShonnoh and ends with Simchas Torah. Each day is another stage in that process. It is a cosmic development, which is reflected within each and every one of us and is hinted at in the above verse– “and you shall know today and internalise that G-d is L-rd in the heavens above and on the earth below, there is no other”.
The Zohar says that היום is often includes a hidden reference to ראש השנה. וידעת היום - “and you shall know today” alludes to Rosh HaShonnoh. Rosh HaShonnoh is the beginning. We start with a ידיעה –‘knowledge’: G-d is King. With that knowledge, we, as it were, crown G-d. It is the שמע ישראל of the year. A proclamation of G-d’s kingship.
This can be seen too using gematrioh. וידעת היום is gematrioh שמע ישראל ד' אלקינו ד' אחד, which is gematrioh נזר ראש השנה [the coronet of Rosh HaShonnoh] which is gematrioh כתר מלכות [the Crown of Kingship].
This כתר מלוכה is the beginning. It is the בת היתה לאברהם ובכל שמה (“Avrohom had a daughter; her name was: ‘in-everything’”) which the commentaries explain to mean that Avrohom crowned G-d over the whole world; he proclaimed His Name wherever he went, thus causing the revelation of the Divine Presence and inviting, as it were, G-d, once again to dwell on earth with man. (Since he gave his life over to G-d, the Divine Presence ‘dwelt’ with him. This is what is meant by ‘a daughter’.)
Thus the רא"ש השנה – the ‘head’ of, or letters before, השנ"ה – are gematrioh אברהם.
The next Yom Tov is Yom Kippur. Yom Kippur is the heart. It is the ברוך שם כבוד מלכותו לעולם ועד of the year – the bringing home of שמע ישראל ד' אלקינו ד' אחד - the proclamation of ראש השנה. It is the והשבות אל לבבך – the internalisation of - וידעת היום – the intellectual idea of G-d’s continuous Providence. Thus, it is the one time in the year we are allowed, nay, instructed, to say ברוך שם כבוד out aloud. The heart is open. Or, more correctly, we are in the heart.
In gematrioh we can see this too. וידעת היום והשבות אל לבבך is gematrioh ofברוך שם כבוד מלכותו לעולם ועד. יום הכפורים (using the system of מנצפ"ך), or alternatively, five times כפור [corresponding to the 5 prayers said on Yom Kippur], is also gematrioh ברוך שם כבוד מלכותו לעולם ועד plus twiceאלקים (- the twice אלקים corresponds to two levels of the Shechinoh which the Zohar explains as the reason for the double expression of כפור in the Torah’s appellation of יום הכפורים).
This latter number is also the gematrioh of יצחק when spelt out full [במלוי]. This is because יום הכפורים is the root and strength of the attribute of Yitschok [אילו של יצחק]. Yitschok represents complete purity and holiness. He is the light [יצחק is gematrioh אור – light] revealed within darkness, bitterness made sweet. This is the power of Teshuvoh and of Yom Kippur.
So now, through Rosh HaShonnoh and Yom Kippur, we have internalised that G-d is our king. The next step is to fully integrate within our psyche that He is “L-rd in the heavens above and on the earth below, there is no other”. This is done through Sukkos till Simchas Torah.
סוכה is gematriah האלקים. Sukkos is a festival that revisits the sublime atmosphere and aura of the השגחה and Shechinoh that was with the Jews in the wilderness. The name of that השגחה and Shechinoh is האלקים. האלקים/סוכה is also gematriah the two names of G-d, the Ineffable Name and the Name that describes His mastery over each person – Adon-y, which means My Master. These two Names, when combined, describe the transcendence of G-d, beyond nature and time, that is to be found in this world and with every person. This is the mindset that the Sukkah drives home, through the Mitsvos of the Four Species. Thus וידעת היום והשבת אל לבבך כי ד' הוא האלקים is gematrioh סוכה – לולב, אתרוג, 2.ערבה, 3.הדס.
This is the Yom Tov of Yaakov. Thus יעקב is gematrioh twice סוכה for he connected two ‘Sukkos’, the Divine Presence that is in heaven to the Divine Presence that is on Earth.
Finally, on Hoshana Rabboh, we pray not only for the world’s peoples, livestock, produce etc, but most importantly, for the final redemption. This is carried through in our ecstatic dancing on Sh’mini Atseres and Simchas Torah where we get a taste of the dance of the future, where the righteous will dance as it were in a circle round the Holy One, blessed be He, that is to say, His Divine Presence will be clear for all to see.
Then we will all see clearly, as at the time of the exodus from Egypt and the Giving of the Torah, that “G-d is L-rd in the heavens above and on the earth below, there is no other”. Thus, הושענא רבא שמחת תורה is gematriah בשמים ממעל ועל הארץ מתחת אין עוד.
A Simchas Yom Tov and a good Kvittel.
 (דברים ד, לט)
 שער הכוונות, דרושי סוכות
 Deut. 4:39.
 For those interested in gematrias, here is the calculation: For וידעת היום we use the system of מנצפ"ך whereby the final ם equals 600. Thus וידעת היום equals 1111 [itself an interesting number, expressing G-d’s one-ness in all the integers, i.e. the four worlds], with the 9 letters = 1120, minus the כולל for each number = 1118 - the gematrioh of שמע ישראל ד' אלקינו ד' אחד. This is gematrioh נזר ראש השנה which is gematrioh כתר מלכותwith 2 כוללים.
 Midrash, Chayei Soroh, on the verse: (בראשית כד, א) וד' ברך את אברהם בכל – “And G-d blessed Avrohom with everything” (Gen. 24:1)
 Ramban, ibid., Rashbo, Rabbeinu Bachye, among others.
 i.e. יו"ד צדי"ק ח"ת קו"ף
 This is the secret hinted at in the honey Shimshon HaGibor extracted from the lion [see Shoftim 14:14].