When do the 11 months of Kaddish for a parent end?

I'm sharing this with permission of R Akiva Males
 
Here's how he wrote it to his congregant:
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Hi YYYYY, I hope you're well.
 
While researching your Kaddish question & I found different answers.
 
As such, I reached out to Rabbi Gedalia Dov Schwartz in Chicago (he's the head of the RCA's Beit Din as well as the Beit Din of the Chicago Rabbinical Council) for guidance.
 
Here's what he told me:
 
When we say that a child stops reciting Kaddish for a parent after 11 (Hebrew) months, that means Kaddish concludes after the child has recited the Kaddish for that parent for a full 11 months.

As such, the 11 months are counted from the burial -- when Kaddish was first recited -- and not from the date of death (unless the person was buried on the same day he/she died).
 
The Yahrtzeit, however, is the day the parent died.
 
[He added that a Yahrtzeit is always observed on the Yom HaMitah unless the Yom HaKevurah took place 3 daysafter the death.]

As such:
 
Your mother passed away on 1 YYYYYY.
 
She was laid to rest on 2 YYYYYY.
 
That means that Kaddish was first recited for your mother on 2 YYYYYY.
 
As such, a full 11 months of reciting Kaddish for her would be completed at sundown on 1 XXXXXXX.
 
I hope this helps.
 
 
Sincerely,
Rabbi Akiva Males
Kesher Israel Congregation
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Shalom,
RRW