33

• If the 6000 years are 50 "days", the 33rd day was the one in which Rashbi lived, a private revelation of Kabbalah, part of which took place, per tradition, on the 33rd day of the Omer, on Rashbi's Yartzheit.
• The 33rd Yovel cycle from the time of Ezra haSofer was the time in which the Zohar was published, a more public revelation of Kabbalah.  See here for review.
• After the 33rd day of Dam Tohar, a mother who has given birth to a boy comes to the Temple, a level of revelation which wasn't available in the prior two cases.

Kabbalah is grounded in the Sefirah of Yesod, and at 2/3 through Yesod is Ateret haYesod.  The 2/3 point of 50 days (for the first two cases above) symbolizes this switch to Ateret haYesod at 33.  The third case, however, is dealing with 40 days total.  How is it related to Ateret haYesod?  Because it is actually referring to the precise timing of the switch to Ateret haYesod, which is a time for the higher levels of revelation from the side of prophecy.  This time is equivalent to the 2/3 point mentioned in Zohar VaYera, in which the Zechirah takes place.