Kropotkin birth date history question, especially for Russian speakers

Hi all, would really appreciate your help with this.
But we are trying to work out the exact birthday of Peter Kropotkin.
We believed it to be 21 December 1842 in the new style calendar, which translated to 9 December 1842 in the old style calendar used at the time. This was according to sources like Encyclopaedia Britannica – for whom Kropotkin wrote himself – in the entry written by Martin A. Miller and Paul Avrich: https://www.britannica.com/biography/Peter-Alekseyevich-Kropotkin/additional-info#history
While other places like the Boris Yeltsin library, say that his birthday was 9 December new style/27 November old style: https://www.prlib.ru/en/history/619795
If anyone knows definitively one way or the other, or has any sources in Russian from before the dating system changed, please let us know!

There is no question that

There is no question that Peter Kropotkin was born on December 9, 1842 new style. In fact there were celebrations on this date throughout Western Europe and America during his lifetime. December 21, 1842 new style was the date of his christening,

Karetelnik wrote: There is no

Karetelnik

There is no question that Peter Kropotkin was born on December 9, 1842 new style. In fact there were celebrations on this date throughout Western Europe and America during his lifetime. December 21, 1842 new style was the date of his christening,

Thanks, that's what it is looking like to us now. And perhaps the christening date is where the confusion came from in other sources.
Do you know of any decent – probably Russian language – sources we can use to definitively confirm that?
As we would like to update our own archive, but also get Encyclopaedia Britannica and Wikipedia to correct their entries, which they won't do without good sources.
(We did find French articles while Kropotkin was alive about birthdays on 9 December, but weren't sure if he might have still celebrated on that date even though it was potentially the old style date.)

I suggest the Great Soviet

I suggest the Great Soviet Encyclopedia, 3rd edition. The entry for Kropotkin can be found here: http://irkipedia.ru/content/kropotkin_pyotr_alekseevich_bolshaya_sovetskaya_enciklopediya_3_e_izd_1969_78 and was written by Natalia Pirumova, author of a much-admired biography of Kropotkin. The publication of her book in 1972 is recognized as a significant event in the history of the Soviet period.

Kropotkin birth date history question, especially for Russian speakers

There is no question that

Karetelnik wrote: There is no

I suggest the Great Soviet

Great, thanks