TIME & CALENDARS

Sidereal day vs. solar day

Sidereal day vs. solar day

Sidereal day: a day with respect to the stars.

Solar day: a full rotation with respect to the sun.

Difference is arising from 0.986ْ motion of Earth every day.

It will take 0.986ْ/day )1440 min/360ْ (= 3.943 = 3 min 56 s /day extra time

Since 1 day = 24 h x 60 min = 1440 min.

Time Zones

Midnight Sun

The midnight sun is a natural phenomenon occurring in summer months at latitudes north and nearby to the south of theArctic Circle, and south and nearby to the north of the Antarctic Circle where the sun remains visible at the local midnight. Given fair weather, the sun is visible for a continuous 24 hours, mostly north of the Arctic Circle and south of the Antarctic Circle. The number of days per year with potential midnight sun increases the farther poleward one goes.

Midnight Sun

 Canada (Yukon, Northwest Territories, andNunavut), 

United States of America (Alaska),  Denmark(Greenland),  Norway,  Sweden,  Finland,  Russia, Extremities of Iceland.

Leap years

One solar year is 365.242190402 days Leap year: A year in which a 366 day is

added. Julian Calendar: The calendar with normal

years with 365 days, and leap years every 4th year without exception.

Gregorian Calendar: The calendar in current use, with normal years with 365 days, and leap years every 4th year, except for years that are divisible by 100 but not by 400 years.

Example

Classify the following years into normal or leap:1990, 1992, 1900, 2000, 1800, 1600, 2010,

2100 Normal years: 1990, 1900, 1800, 2010,

2100 Leap years: 1992, 2000, 1600

Julius Caesar Augustus Caesar Gregorian Calendar started 1582 (1600

years after Julian calendar) The error has grown to 10 days. To bring calendar in synchrony with

seasons, 10 days were eliminated from the year

The day after Oct. 4 was Oct. 15th 1582

Adopted in UK 1752 Russia early 20th century a.m. = ante meridian p.m. = post meridian B.C. = before Christ 1 B. C. is it the year of his birth, or the next

year? A. D. after death A. D. = anno Domini (The year of the Lord).

Origin of Month names

January Janus, the god of the doorway, a two faced god looking to the past and to the future

February februum, which means purification

March The god Mars

April Goddess of love

May Greek goddess Maya

June Junius, an old roman noble family

July Julius Caesar

August Augustus Caesar

September

Seventh month

October Eighth month

November

Ninth month

December

Tenth month

Lunar Calendar

354 d 8h 48m A Lunar year = 354 days or 355 days A Lunar month = 29 days or 30 days

Lunar Monthes :فيها القتال حرم التي الحرم األشهر أحد .مـــحـــرم. للحرب: : أهلها من تخلو أي تصفر كانت العرب ديار أن قيل صــفــر : العشب وظهور الربيع فصل في االسم بهذا سميا اآلخر وربيع األول .ربيع : األولى جمادى إال مذكرة العربية األشهر جميع والثانية األولى جمادى

خمسة،. جمادى باسم اإلسالم قبل يسمى األولى جمادى وكان واألخرىالماء جمد حيث التسمية وقت الشتاء في لوقوعه جمادى .وسمي

:وال القتال، بترك الشهر هذا يعظمون الجاهلية في العرب كان رجـــب. . وعظمه هابه أي الشئ رجب من واسمه فيه يستحلونه

:في عنها قعودها بعد لإلغارة الشهر هذا في القبائل تشعبت شــعــبــانرجب.

. الحر: شدة هي والرمضاء والرمض، الحر زمن وافق رمــضــان : :التسمية وقت ترفعها أي بأذنابها تشول كانت اإلبل ان قيل شـــوال

: . وقيل : وجفافها نقصانها أي اإلبل، ألبان لتشويل وقيل لإلخصاب طلباوإدباره الحرارة درجة االرتفاع .شوال

: . : : وقيل األسفار عن فيه يقعدون كانوا العرب ان قيل الــقــعــدة ذوالحرم األشهر من ألنه القتال عن .قعودهم

. : الحج شهر هو الــحــجــة ذو