Aloysius Lilius (c. 1510 –
1576), also variously
referred to as Luigi Lilio,
Luigi Giglio, or Aluise
Baldassar Lilio, was an
Italian doctor, astronomer,
philosopher and
chronologist, and also
the "primary author"
who provided the proposal
that (after modifications)
became the basis of the
Gregorian Calendar reform of
1582
The crater Lilius on the
Moon is named after him. In
computer science, the Lilian
date is the number of days
since adoption of the
Gregorian Calendar, on 15
October 1582.
Life and work
Not much is known about the
early life of Lilius/Lilio/Giglio.
It is known that he came
from Calabria, Italy, from
Cirò (or Zirò). He studied
medicine and astronomy in
Naples, after which he
served Earl Carafa. He
settled in Verona and died
in 1576.
Although he was still alive
at the time when his
proposal was presented at
Rome, it does not seem that
he made the presentation, it
was handled by his brother
Antonio, also a physician
and astronomer.
He is primarily known as
the "first author" of the
Gregorian Calendar:
he wrote the proposal on
which (after modifications)
the calendar reform was
based.
Lilio's brother Antonio
presented the manuscript to
Pope Gregory XIII; it was
passed to the calendar
reform commission in 1575.
The commission issued a
printed summary entitled
Compendium novae rationis
restituendi kalendarium
(Compendium of a New Plan
for the Restitution of the
Calendar), printed 1577 and
circulated within the Roman
Catholic world in early 1578
as a consultation document.
Lilio's manuscript itself is
not known to have survived;
the printed 'Compendium' is
the nearest known source for
the details it contained.
The processes of
consultation and
deliberation meant that
the reform to the calendar
did not occur until 1582,
six years after the death of
Luigi Lilio in 1576.
The reform had by then
received some modifications
in points of detail by the
reform commission, in which
one of the leading members
was Christopher Clavius;
Clavius afterwards wrote
defences and an explanation
of the reformed calendar,
including an emphatic
acknowledgement of Lilio's
work, especially for his
provision of a useful reform
for the lunar cycle: "We owe
much gratitude and praise to
Luigi Giglio who contrived
such an ingenious Cycle of
Epacts which, inserted in
the calendar, always shows
the new moon and so can be
easily adapted to any length
of the year, if only at the
right moments the due
adjustment is applied." The
papal bull ("Inter
gravissimas") was issued on
February 24, 1582, ordering
Catholic clergy to adopt the
new calendar, and exhorting
Catholic sovereigns to do
the same.
Year 2010 is the 500th year
since the Astronomer birth
date and several activities
have been organized (by
Italian astronomers) in
order to recognize the great
work performed by Luigi
Lilio. In particular, in
Torretta di Crucoli(Crotone,
Italy), a new astronomical
group has been created and
entitled to Luigi Lilio:
Circolo Astrofili Luigi
Lilio Torretta (C.A.L.L.T.)
