According to some scholars, Marcus Aurelius first day of reign is March 8th 161. But, indeed, it is the day before (i.e. March 7th) when Antoninus Pius dies, leaving the power to his successor. In fact, we have some details about the transition.
For instance, we know that two days before his passing Antoninus Pius is at his ancestral estate at Lorium (Etruria). This location is about 19 kilometres (12 mi) from Rome. We are also aware that Antoninus Pius likes Alpine cheese and that he enjoys it on that evening. Perhaps he enjoys too much of his favorite dairy product. In fact, he vomits on the same night. And he has a fever the next day (March 6th). The day after, March 7th 161, he summons the imperial council and passes the state and his daughter to Marcus. The emperor seals his life with the last word he pronounces when the tribune of the night-watch comes to ask for the password – <aequanimitas> (equanimity). He then turns over, as if going to sleep, and passes away. His death closes the longest reign since Augustus, exceeding Tiberius by a couple of months.
We commemorate Marcus Aurelius first day of reign because he is the author of the “Meditations“. It is an assemblage of observations, comments and thoughts which all reflects the Stoic approach of this Emperor philosopher. As an example, “to live the good life: we have the potential for it. If we can learn to be indifferent to what makes no difference“.
Another popular quotation is the following: “Remember this – Matter: how tiny your share of it. Time: how brief and fleeting your allotment of it. Fate: how small a role you play in it“. For other details see also the page Marcus Aurelius Antoninus Augustus in the MASTERS section of this website.