Gregorian Calendar introduced - October 15, 1582

On this day in 1582, Pope Gregory XIII introduced the Gregorian calendar, which was created as a way to reform the Julian calendar. 

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Episode Transcript

Speaker 1 (00:00):
This Day in History Class is a production of I
Heart Radio. Hi everyone, I'm Eves and welcome to This
Day in History Class, a podcast where we rip out
a page from the history books. Every day. Today is
October nineteen. The day was October two. Pope Gregory introduced

(00:29):
the Gregorian calendar as a way to reform the Julian calendar.
The previous day was October four on the Julian calendar.
Until the end of the twenty one century, the Julian
calendar is thirteen days behind the Gregorian calendar. The Gregorian
calendar is used in most of the world today. There's

(00:50):
a leap year. Every four years. On the Julian calendar,
an extra day is added to the month of February,
so that the year is three hundred and sixty six
days long. That means the Julian solar year is about
three hundred and sixty five and one fourth days long,
But the solar year is slightly shorter than that. It
comes in at approximately three hundred and sixty five point

(01:13):
two four two days. Broken down, that's about three hundred
and sixty five days, five hours, forty eight minutes, and
forty five seconds. Because the Julian year was about eleven
minutes longer than the mean solar year. The date of
the equinox, according to the Julian calendar, was many days
off from the observed date of the equinox. In reality,

(01:37):
that in turn caused dates on the religious calendar to
be skewed, since the date of Easter was based on
the Northern Hemisphere spring equinox. People were aware of this
drift and that calendar reform was needed for centuries before
the Gregorian calendar was introduced, but previous attempts to change
the calendar filled through. Still, the need to update the

(02:01):
calendar became more urgent. In its fifteen sixty two to
fifteen sixty three session, the Council of Trent called for
Pope Paul the Third to reform the calendar. The plan
was to change the date of the vernal or spring
equinox back to March one, which was the date of
the equinox that was fixed by the Church at the

(02:21):
time of the Council of Naucia, and it took until
fifteen eighty two for the change to happen, when Pope
gregoryte a papal bull authorizing a reformed calendar. Gregory's reforms
were based on the research and suggestions of Italian scientists
Aloisius Lilius and German mathematician Christopher Claudius. October four eighty

(02:46):
two on the Julian calendar was followed by October on
the Gregorian calendar, with no change in the continuity of
week days. The Church chose October so it could avoid
disrupting any major Christian celebra rations. On the Gregorian calendar,
no century year is a leap year unless it's divisible
by four hundred. This helps ensure the calendar year is

(03:09):
nearly the same length as the solar year. Much of
Roman Catholic Europe adopted the new calendar within a year,
but Protestant and Orthodox states were slow to follow. The
Protestant German states switched in sixte Britain and its territories
made the change in seventeen fifty two, and from there

(03:30):
more countries around the world adopted the Gregorian calendar until
its use was widespread, though many countries in Eastern Europe
used the Julian calendar into the twentieth century. Though the
Gregorian calendar is the international standard, some countries use other calendars,
and people have proposed reforms to the Gregorian calendar. I'm Eaves, Jeffcode,

(03:54):
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(04:16):
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