Q:

(How) is Chai Elul observed in Chassidic communities?

I have a wall calendar (source forgotten) that, as is typical for Jewish calendars, marks the parshiyot for each Shabbat.  Next week, instead of giving the name of the parsha (Ki Tavo) it says "Chai Elul".  Yes ok, I thought, next Shabbat is the 18th of Elul, but so what?  I asked Google what this day is about and learned that this date is important in Chassidism as the birthday of both the Baal Shem Tov and the Alter Rebbe.
This calendar marks other special days without affecting the parsha "slot", so this wasn't the only place they could have noted it.  That they replaced "Ki Tavo" with "Chai Elul" made me wonder if there's something special about the torah reading on that day in Chassidic communities.  I didn't find anything in my search about special observances for the day, either as part of the torah service or more generally.
What do Chassidic communities do to mark this day?  Does it affect the torah service?

A:

Chabadpedia has an article.

מעת אשר נתפרסם אשר יום השמונה עשר בחודש אלול הוא יום ההולדת של הבעש"ט
  ושל רבינו הזקן - נהגו, בכמה מקומות ובפרט בבתי כנסיות חב"ד, לעשות אותו
  יום-התוועדות בסיפור מעשי צדיקים, חיזוק בדרכי החסידים בכלל ואהבת ישראל
  בפרט וקבלת החלטות בקביעות עתים ללימוד התורה - הנגלה והנסתר. בהתעוררות
  מיוחדה חוגגים יום הולדת זה בבית הרב, והאדמו"ר אומר דברי התעוררות בתורה
  ועבודה, ולפעמים - גם מאמר חסידות
(my translation)
The 18th of Elul is the birthday of the Baal Shem Tov and of Rabbi
  Shneur Zalman of Liadi. The custom is in many places and especially in
  Chabad shuls to make a get-together, telling stories of righteous
  people, strengthening the participants in Chassidus, especially loving
  Jewish people and making resolutions to devote time to learning the
  Torah including Kabbalah.

