As it appears to me, no real astronomical event such as eclipse, or conjunctions, or different phases of the moon, or heliacal rising
And yet, the heliacal rising
of Sirius that occurred on or about a certain specific date every year would actually move forward one day every four years with the clerical 365-day calendar of the Egyptians, so that by the time of the post-Alexandrian pharaohs it was deemed so badly in need of reform that, once and for all, the ecclesiastic year was decreed that it should conform with the civil year.
In modern times, how many of us who enjoy the Dog Nights of winter, observing Sirius on February evenings, also try to look for the heliacal rising
of Sirius at August dawns?
Finally, Luft presents a short essay on the absolute date for the heliacal rising
of Sothis in year 7 of Sesostris III recorded in the Lahun archive.
Unfortunately their 365-day solar calendar had no leap days, so it eventually fell far out of step with the seasons and the heliacal rising
In traditional Maori society, a watchful eye is kept on the evening sky following the heliacal rising
of Matariki to spot the appearance of the next new Moon.
The line coincides with summer solstice on Mars 500,000 years ago, and the same vista incorporates the heliacal rising
The ancient Egyptians marked the start of their new year by the heliacal rising
(first appearance in the glow of sunrise) of Sirius.
Because the count was roughly a quarter-day short of the true length of the year, the heliacal rising
of Sirius drifted through the solar calendar and did not recur on the first day of the year until 1,461 of those 365-day years had elapsed.
the heliacal rising
(in the eastern skies) to an astrologer.
They assigned that seasonally significant heliacal rising
to July 3rd, the eve of American Independence Day.
These chunks of computer instructions can be included in earlier programs - for telescopic limiting magnitudes (S&T: November 1989, page 522), heliacal rising
(S&T: September 1985, page 261), lunar occultations (S&T: January 1993, page 89), and extinction angles (S&T: April 1987, page 426) - to yield more accurate results.