  In the context of the recently proposed contact-binary model (Sekanina 2021),
I investigate the circumstances of the first perihelion passage of the Kreutz
sungrazers in orbits with barycentric periods near 735 yr, following the
initial near-aphelion splitting of the presumed progenitor, Aristotle's comet
of 372 BC. Given favorable conditions at this breakup and at episodes of
secondary fragmentation in its aftermath, the fragments should have arrived at
their first perihelion nearly simultaneously, reminiscent of the anticipated
outcome for the two-superfragment model's perihelion return of AD 356 (Sekanina
& Chodas 2004). The relevant case of a swarm of Kreutz sungrazers is examined
to appraise possible scientific ramifications of the brief remark by Ammianus
Marcellinus, a Roman historian, that "in broad daylight comets were seen" in
late AD 363, only seven years later. The tested scenario, which does not
contradict Ammianus' narrative and is consistent with the contact-binary model,
involves a set of ten sungrazers visible in the daytime, all reaching
perihelion over a period of 4.6 days. As part of this work, I comment on the
role of the rapidly developing, brilliant post-perihelion tail; revise the
apparent magnitude typical for the first and last naked-eye sightings; compare
the visibility conditions in full daylight, in twilight, and at night; and, for
the first time, present circumstantial evidence that favors comet X/1106 C1 as
the parent to C/1843 D1 rather than to C/1882 R1 and C/1965 S1.
