Page 132 - NUMINO Challenge_B2
P. 132
Basic Concepts Changes due to Leap Years
There are 365 days in a year and 365 7 52 r1. Therefore, any date this year
will be one day later the next year. If the 1st of January is a Sunday this year,
then the 1st of January of next year will be a Monday. But note that the 1st of
January and the 31st of December of the same year will be on the same day.
Years that have 366 days are called leap years. Leap years come once every
four years: 2004, 2008, 2012, etc. Years that come once every 100 years, such
as 1700, 1800, 1900, etc. are not leap years. But years that come once every
400 years, such as 1600, 2000, 2400, etc. are leap years.
Example January 14, 2008 is a Monday. What day is January 17, 2009?
(2008 is a leap year.)
Class Notes
Since there are 7 days in a week, each day comes once every days. Year 2008 has
days because it is a leap year. 7 r 2. Therefore, after a
year, today becomes days from today.
Since January 14, 2008 is a Monday, January 14, 2009 will be a .
Therefore, January 17, 2009 will be a .
The Origin of Calendars
2000 years ago, the Roman calendar only had 355 days. Each year, the calendar would be off by
ten days. Around the 1st century BC, Julius Caesar decided to use the Egyptian solar calendar, that
had 365 days a year. But there are not exactly 365 days in a year. It is closer to 365.2421 days;
therefore, a leap year with 366 days is added every four years to compensate.
This calendar is called the Julian calendar, named after Julius Caesar, and was widely used in
Europe for 1500 years. In 1582, Pope Gregory the 8th removed three leap years from every 400
years. Therefore, the 1st year of every century: 1700, 1800, 1900, etc. is not a leap year but the
years that come every 400 years, 1600, 2000, 2400, etc. are leap years. This is the Gregorian
calendar that is used by most countries today.
129Communication
There are 365 days in a year and 365 7 52 r1. Therefore, any date this year
will be one day later the next year. If the 1st of January is a Sunday this year,
then the 1st of January of next year will be a Monday. But note that the 1st of
January and the 31st of December of the same year will be on the same day.
Years that have 366 days are called leap years. Leap years come once every
four years: 2004, 2008, 2012, etc. Years that come once every 100 years, such
as 1700, 1800, 1900, etc. are not leap years. But years that come once every
400 years, such as 1600, 2000, 2400, etc. are leap years.
Example January 14, 2008 is a Monday. What day is January 17, 2009?
(2008 is a leap year.)
Class Notes
Since there are 7 days in a week, each day comes once every days. Year 2008 has
days because it is a leap year. 7 r 2. Therefore, after a
year, today becomes days from today.
Since January 14, 2008 is a Monday, January 14, 2009 will be a .
Therefore, January 17, 2009 will be a .
The Origin of Calendars
2000 years ago, the Roman calendar only had 355 days. Each year, the calendar would be off by
ten days. Around the 1st century BC, Julius Caesar decided to use the Egyptian solar calendar, that
had 365 days a year. But there are not exactly 365 days in a year. It is closer to 365.2421 days;
therefore, a leap year with 366 days is added every four years to compensate.
This calendar is called the Julian calendar, named after Julius Caesar, and was widely used in
Europe for 1500 years. In 1582, Pope Gregory the 8th removed three leap years from every 400
years. Therefore, the 1st year of every century: 1700, 1800, 1900, etc. is not a leap year but the
years that come every 400 years, 1600, 2000, 2400, etc. are leap years. This is the Gregorian
calendar that is used by most countries today.
129Communication
