SpaceWatchtower: April 2023

Monday, April 17, 2023

LIVE-STREAM: Rare Hybrid Solar Eclipse Early Thur. Morning

NO PARTIAL PHASE OF ANY SOLAR ECLIPSE / ECLIPSE OF THE SUN, NOR ANY ANNULAR SOLAR ECLIPSE / ANNULAR ECLIPSE OF THE SUN, IS SAFE TO LOOK AT DIRECTLY, UNLESS YOU HAVE THE PROPER TRAINING AND PROPER EQUIPMENT TO DO SO SAFELY; OTHERWISE EYE-SIGHT COULD BE DAMAGED PERMANENTLY !!! This graphic shows one way to safely view the partial phases of a Solar Eclipse / Eclipse of the Sun, or safely view an Annular Solar Eclipse / Annular Eclipse of the Sun, by building a Solar Pinhole Viewing Box (a.k.a. Pinhole Camera) as shown above. After building this box, you must turn your back to the Sun and allow the light from the Sun to go through the pinhole and shine on a white piece of paper on the other end of the inside of the box (NEVER LOOK THROUGH THE PINHOLE AT THE SUN!).
(Graphic Source: Eric G. Canali, former Floor Operations Manager of the original Buhl Planetarium and Institute of Popular Science / Buhl Science Center, America's fifth major planetarium and Pittsburgh's science and technology museum from 1939 to 1991, and Founder of the South Hills Backyard Astronomers amateur astronomy club.)

More Information - SOLAR ECLIPSE / ECLIPSE OF THE SUN: TIPS FOR SAFE VIEWING –

Link >>> https://buhlplanetarium2.tripod.com/FAQ/soleclipse/solareclipseviewingtips.html

By Glenn A. Walsh

Reporting for SpaceWatchtower

Early Thursday morning (2023 April 20), a rare Hybrid Solar Eclipse / Hybrid Eclipse of the Sun (both Total and Annular Solar Eclipse / Eclipse of the Sun) will be visible, weather-permitting, just north and west of Australia. A Live-Stream Internet Web-Cast of the event will be available for those not in the area of the eclipse, or if inclement weather prevents direct viewing of the event.

NEVER LOOK DIRECTLY AT ANY SOLAR ECLIPSE / ECLIPSE OF THE SUN, UNLESS YOU HAVE THE PROPER TRAINING AND PROPER EQUIPMENT TO DO SO SAFELY; OTHERWISE EYE-SIGHT COULD BE DAMAGED PERMANENTLY !!!

Internet link to Live-Stream Web-Cast of 2023 April 20 Hybrid Solar Eclipse / Hybrid Eclipse of the Sun near the end of this blog-post.

WHERE CAN THIS ECLIPSE BE SEEN ?

The path of the 2023 April 20 Hybrid Solar Eclipse / Hybrid Eclipse of the Sun will run from the southern portion of the Indian Ocean to just north of Australia (which will just touch the north-western tip of Australia, known as North West Cape, a remote peninsula of Western Australia). This eclipse concludes north and east of Australia. A Partial Solar Eclipse / Partial Eclipse of the Sun will be visible, weather-permitting, just beyond the confines of the Hybrid Solar Eclipse / Hybrid Eclipse of the Sun.

This eclipse will appear as a Total Solar Eclipse / Total Eclipse of the Sun in the North West Cape Peninsula and Barrow Island of Western Australia, close to the middle of the Eclipse Path. This eclipse will appear as an Annular Solar Eclipse / Annular Eclipse of the Sun. at the beginning of the Eclipse Path (at and near local Sunrise) and at the end of the Eclipse Path (at and near local Sunset).

WHEN CAN THIS ECLIPSE BE SEEN?

This rare Hybrid Solar Eclipse / Hybrid Eclipse of the Sun will be visible, weather-permitting, early on Thursday Morning, 2023 April 20. Although eclipse times will vary for specific locations, the following are the general times for this eclipse. Times are given in Coordinated Universal Time (UTC), the international time used by scientists; subtract 4 hours from the times given for Eastern Daylight Saving Time (EDT) or subtract 5 hours from the times given for Eastern Standard Time (EST). ---

First location to see Partial Eclipse begin: 1:34:26 UTC

First location to see Full Eclipse begin: 2:37:08 UTC

Time of Primary Lunar Phase of New Moon (Lunation #1241): 4:12 UTC

Greatest Eclipse: 4:16:46.8 UTC

Last location to see Full Eclipse end: 5:56:43 UTC

Last location to see Partial Eclipse end: 6:59:22 UTC

WHAT IS ---

A Solar Eclipse / Eclipse of the Sun ?

A Solar Eclipse / Eclipse of the Sun occurs when the Moon comes directly between the Sun and the Earth and part or all of the lunar shadow falls on a portion of our planet. Any Solar Eclipse / Eclipse of the Sun is dangerous to eye-sight to view directly, unless you have the proper training and proper equipment to do so safely! A Solar Eclipse / Eclipse of the Sun always occurs near and at the time of a Primary Lunar Phase of New Moon.

A Total Solar Eclipse / Total Eclipse of the Sun ?

A Total Solar Eclipse / Total Eclipse of the Sun occurs when the Path of the Eclipse includes a Path of Totality, where the Moon completely obscures the Sun for a short length of time for a particular location on the Earth which is within the Path of Totality. At the time of Totality, darkness similar to a deep level of dusk falls on that location, and sometimes scientists with special observing equipment can view Solar Flares and / or Prominences emanating from the Sun. With direct Sunlight completely blocked, the air temperature generally declines noticeably, and birds and other wildlife often begin their night-time routines.

An Annular Solar Eclipse / Annular Eclipse of the Sun ?

An Annular Solar Eclipse / Annular Eclipse of the Sun is somewhat similar to a Total Solar Eclipse / Total Eclipse of the Sun. However, unlike a Total Solar Eclipse / Total Eclipse of the Sun, the Sun is never completely covered by the Moon, for a location in the Path of Annularity, during an Annular Solar Eclipse / Annular Eclipse of the Sun. And, like during a Total Solar Eclipse / Total Eclipse of the Sun, the natural light level acts almost like at dusk, the air temperature generally declines noticeably, and birds and other wildlife are confused and may begin their night-time routines during an Annular Solar Eclipse / Annular Eclipse of the Sun.

During an Annular Solar Eclipse / Annular Eclipse of the Sun while in the Path of Annularity, the Moon blocks-out the vast majority of the Sun, except for the extremely bright edge of the solar disk. Hence, this type of eclipse is often referred to as a “Ring-of-Fire” Solar Eclipse / "Ring-of-Fire" Eclipse of the Sun, as the bright edge appears as a ring-of-fire around the dark Moon.

The reason an Annular Solar Eclipse / Annular Eclipse of the Sun does not completely block-out the Sun's light, as does a Total Solar Eclipse / Total Eclipse of the Sun, is because during an Annular Solar Eclipse / Annular Eclipse of the Sun the Moon is farther from Earth than normal and appears a little smaller as viewed from Earth. Hence, the Moon is too far, and appears too small, to block-out the entire solar disk.

A Hybrid Solar Eclipse / Hybrid Eclipse of the Sun ?

A Hybrid Solar Eclipse / Hybrid Eclipse of the Sun occurs when the eclipse begins as an Annular Solar Eclipse / Annular Eclipse of the Sun, during the middle of the Eclipse Path transitions to a Total Solar Eclipse / Total Eclipse of the Sun, then transitions back to an Annular Solar Eclipse / Annular Eclipse of the Sun as the Eclipse Path ends.

A Partial Solar Eclipse / Partial Eclipse of the Sun ?

A Partial Solar Eclipse / Partial Eclipse of the Sun occurs when only part of the Sun is blocked by the Moon. This is also true during the Partial Phases of a Total, Annular, or Hybrid Solar Eclipse / Total, Annular, or Hybrid Eclipse of the Sun. Usually, more of the Sun is still visible during a Partial Solar Eclipse / Partial Eclipse of the Sun (and during the Partial Phases of other Solar Eclipses / Eclipses of the Sun) than during an Annular Solar Eclipse / Annular Eclipse of the Sun or Hybrid Solar Eclipse / Hybrid Eclipse of the Sun.

There is no time during an Annular Solar Eclipse / Annular Eclipse of the Sun, or during a Partial Solar Eclipse / Partial Eclipse of the Sun (or during the Partial Phases any Solar Eclipse / Eclipse of the Sun), when it is safe to look directly at the eclipse, unless you have the proper training and proper equipment to do so safely!

ECLIPSE PAIRS ---

Eclipses always come in pairs, and sometimes three in-a-row. A Lunar Eclipse / Eclipse of the Moon either precedes a Solar Eclipse / Eclipse of the Sun by a couple weeks, or a Lunar Eclipse / Eclipse of the Moon follows a Solar Eclipse / Eclipse of the Sun by a couple weeks.

This time, a Penumbral Lunar Eclipse / Penumbral Eclipse of the Moon follows on Friday Afternoon, 2023 May 5. This eclipse can be viewed directly [any Lunar Eclipse / Eclipse of the Moon is safe to view with the naked-eyes (one-power), binoculars, or a telescope] from the Indian Ocean, Africa, Eastern Europe, Asia, Australia, and New Zealand. However, a Penumbral Lunar Eclipse / Penumbral Eclipse of the Moon is quite dim and often difficult to discern.

HOW TO SAFELY VIEW ANY SOLAR ECLIPSE / ECLIPSE OF THE SUN ---

Internet - Watch the eclipse on an Internet, Live-Stream Web-Cast (Internet link to Live-Stream Web-Cast near the end of this blog-post). Of course, people outside of the Path of an Eclipse can watch the eclipse on an Internet, Live-Stream Web-Cast, as well as people within the Eclipse Path where clouds obscure the view..
Public Observing Events - Sometimes educational events for eclipse viewing are sponsored by a local planetarium or science museum, astronomical observatory, science department of a local college or high school, amateur astronomy club, or local library.
Solar Pinhole Viewing Box - Create a Solar Pinhole Viewing Box (a.k.a. Pinhole Camera), as displayed and described at the beginning of this blog-post.
“Solar Eclipse Glasses” - For a few dollars you can purchase Solar Eclipse Glasses. However, only use such glasses that are specifically labeled for solar eclipse viewing, preferably approved by the American Astronomical Society (to ensure you do not purchase fake eclipse glasses). Special Note: Solar Eclipse Glasses are very fragile and must be handled gently. Also, before each use during an eclipse, check the glasses by looking through the glasses at a lit light bulb; if you find any holes or tears in the glasses, that pair of glasses could damage your eye-sight during eclipse viewing and should be discarded.
Shade Rating Number 14 Welder's Glass – Shade Rating Number 14 Welder's Glass (and only Welder's Glass Rated at Shade Number 14, the strongest shade available) can be used for safe eclipse viewing, but may be uncomfortable to some because the Sun still appears very bright through this glass.

THESE ARE THE ONLY SAFE WAYS TO VIEW ANY SOLAR ECLIPSE / ECLIPSE OF THE SUN !

INTERNET LINK TO LIVE-STREAM WEB-CAST OF 2023 APRIL 20 ECLIPSE:

Link >>> https://www.timeanddate.com/live/eclipse-solar-2023-april-20

SOLAR ECLIPSE / ECLIPSE OF THE SUN: TIPS FOR SAFE VIEWING – Link >>> https://buhlplanetarium2.tripod.com/FAQ/soleclipse/solareclipseviewingtips.html

Internet Links to Additional Information ---

Solar Eclipse: Link >>> https://en.wikipedia.org/wiki/Solar_eclipse

Hybrid Solar Eclipse: Link >>> https://en.wikipedia.org/wiki/Solar_eclipse#Types

Related Blog-Posts ---

Hybrid Solar Eclipse: 2013 Nov. 3.

Link >>> http://spacewatchtower.blogspot.com/2013/11/partial-sunrise-solar-eclipse-sunday.html

Hybrid Solar Eclipse: 2005 April 5.

Link >>> https://buhlplanetarium4.tripod.com/eclipse/hybrid2005.html

Source: Glenn A. Walsh Reporting for SpaceWatchtower, a project of Friends of the Zeiss

Monday, 2023 April 17.

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gaw

Glenn A. Walsh, Informal Science Educator & Communicator (For more than 50 years! - Since Monday Morning, 1972 June 12):
Link >>> http://buhlplanetarium2.tripod.com/weblog/spacewatchtower/gaw/
Electronic Mail: < gawalsh@planetarium.cc >
Project Director, Friends of the Zeiss: Link >>> http://buhlplanetarium.tripod.com/fotz/
SpaceWatchtower Editor / Author: Link >>> http://spacewatchtower.blogspot.com/
Formerly Astronomical Observatory Coordinator & Planetarium Lecturer, original Buhl Planetarium & Institute of Popular Science (a.k.a. Buhl Science Center), America's fifth major planetarium and Pittsburgh's science & technology museum from 1939 to 1991.
Formerly Trustee, Andrew Carnegie Free Library and Music Hall, Pittsburgh suburb of Carnegie, Pennsylvania, the fourth of only five libraries where both construction and endowment funded by famous industrialist & philanthropist Andrew Carnegie.
Author of History Web Sites on the Internet --
* Buhl Planetarium, Pittsburgh: Link >>> http://www.planetarium.cc Buhl Observatory: Link >>> http://spacewatchtower.blogspot.com/2016/11/75th-anniversary-americas-5th-public.html
* Adler Planetarium, Chicago: Link >>> http://adlerplanetarium.tripod.com
* Astronomer, Educator, Optician John A. Brashear: Link >>> http://johnbrashear.tripod.com
* Andrew Carnegie & Carnegie Libraries: Link >>> http://www.andrewcarnegie.cc

* Other Walsh-Authored Blog & Web-Sites: Link >>> https://buhlplanetarium.tripod.com/gawweb.html

Sunday, April 2, 2023

Astronomy Needed to Calculate Dates of Passover & Easter

For centuries, the Primary Phase of Full Moon figured prominently in the annual calculation of the dates of the beginning of Passover and of Easter. (Image Sources: Wikipedia.org , By Gregory H. Revera - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=11901243 )

By Glenn A. Walsh

Reporting for SpaceWatchtower

Each year, Astronomy is used to calculate the date for the beginning of Passover in the Hebrew religion, as well as the date of Easter in the Christian religion. In both cases, the Vernal Equinox which marks the beginning of the season of Spring in Earth's Northern Hemisphere, and the Primary Lunar Phase of Full Moon, are primary parts of the calculation of the two religious festivals.

This year (2023) the Astronomical Vernal Equinox arrived on Monday, March 20 at 5:24 p.m. Eastern Daylight Saving Time (EDT) / 21:24 Coordinated Universal Time (UTC). The first Full Moon following the Vernal Equinox occurs on Thursday, April 6 at 12:34 a.m. EDT / 4:34 UTC. The second Full Moon following the Vernal Equinox will occur on Friday, May 5 at 1:34 p.m. EDT / 17:34 UTC.

This year (2023), the Hebrew festival of Passover (one of the Biblically-ordained Three Pilgrimage Festivals) runs from Wednesday, April 5, beginning at local Sunset, to Thursday, April 13, ending at local Sunset (Internet link to U.S. Naval Observatory web-site, to determine time of local Sunset, near the end of this blog-post).

This year (2023), the Christian festival of Traditional Easter runs (Traditional Easter Holy Week; last week of 40-day Traditional Lent period):

Palm Sunday: Sunday, April 2
Holy Wednesday: Wednesday, April 5
Maundy Thursday / Holy Thursday: Thursday, April 6
Good Friday: Friday, April 7
Holy Saturday: Saturday, April 8
Easter Sunday: Sunday, April 9 (Internet link to U.S. Naval Observatory web-site, to determine time of local Sunrise for Sunrise religious services, near the end of this blog-post):
Easter Monday (2^nd day of Octave of Easter; public holiday in some nations): Monday, April 10

This year (2023), the Christian festival of Orthodox Easter runs (Orthodox Easter Holy Week; last week of 40-day Orthodox Lent period):
Palm Sunday: Sunday, April 9
Great and Holy Wednesday: Wednesday, April 12
Great and Holy Thursday: Thursday, April 13
Good Friday: Friday, April 14
Holy and Great Saturday: Saturday, April 15
Easter Sunday: Sunday, April 16 (Internet link to U.S. Naval Observatory web-site, to determine time of local Sunrise for Sunrise religious services, near the end of this blog-post):
Bright Monday (2^nd day of Bright Week): Monday, April 17

Calculating Date of the Beginning of Passover

Using the traditional Hebrew Calendar, which is a Lunisolar Calendar, the religious festival of Passover begins on the 15^th day of the month of Nisan. In the Gregorian Calendar, this presently occurs between March 26 and April 25.

As Passover is a Spring season festival, it typically begins at local Sunset on the evening before the 15^th day of the month of Nisan. Actually, in the Hebrew Calendar days officially begin at local Sunset and run until the following local Sunset. This comes from the traditional Rabbinic interpretation of the Hebrew Biblical verse, Genesis 1:5 - “There was evening and there was morning, one day.”

Usually, the 15^th day of the month of Nisan begins on the evening of a Full Moon. And, this usually occurs on the first Full Moon after the Vernal Equinox, the official beginning of Spring.

In the Hebrew Calendar, the 1^st day of the month of Nisan marks the beginning of the Lunar New Year. In ancient Israel, the 1^st day of the month of Nisan would not commence until the Barley was ripe. This was the traditional test for the onset of Spring since, at least, the 4^th century.

However, there are times when the Hebrew Calendar includes a Leap-Month. A Leap-Month is inserted into the Hebrew Calendar, to ensure the calendar follows the seasons or Moon phases.

When a Leap-Month in the Hebrew Calendar falls after the Vernal Equinox, sometimes Passover does not begin until the second Full Moon after the Vernal Equinox. The last time this occurred was in the year 2016 of the Gregorian Calendar.

Calculating Date of Easter

Currently, Easter is one of the moveable feasts, with the date determined by a Lunisolar Calendar, similar to the Hebrew Calendar. The difficulty in calculating Easter is due to the fact that our civil calendar does not match astronomical cycles.

A combination of Hebrew, Roman, and Egyptian calendars, along with local culture and customs, all contributed to the Easter calculations we have today. The Egyptians based their calendar on the cycle of the Sun, which was adopted by Roman, and later, Christian cultures. The Hebrew Calendar is based partly on the Lunar Cycle (the Islamic Calendar is also based on the Moon). The Easter calculations become complicated when both lunar and solar calendars are used, combined with the fact that different Christian sects use different mathematical formulas.

Jesus Christ's death and resurrection occurred during the Jewish holiday of Passover (which begins on the night of a Full Moon, immediately after the Vernal Equinox), according to the Christian Bible. However, this led to confusion of what date to celebrate Easter, with Christians celebrating the holiday on different dates.

There was great dissatisfaction expressed by many Christians, in the 3rd and 4th centuries, regarding previous methods of establishing the date of Easter. Originally, they simply used the Jewish festival of Passover and set Sunday of the Passover week as Easter. Some did not like, what they perceived as, the general disorderly state of the Jewish Calendar.

In the year A.D. 325, the First Council of Nicaea of the Roman Catholic Church established only two rules for the annual determination of Easter: independence from the Jewish Calendar and worldwide uniformity. The rules for actual calculation of the date of Easter took centuries to work-out.

Calculating the date of Easter caused several controversies, partly because some Christians did not want Easter to be associated with the Jewish Passover. In at least one case, violence accompanied such a controversy.

The 5^th century astronomer and mathematician, Hypatia of Alexandria, Egypt, was murdered (in March of A.D. 415) by a clique of Bishop Cyril's zealots, according to the Church historian Socrates Scholasticus. According to an unconfirmed hypothesis by Canadian mathematician Ari Belenkiy, she had been attempting to calculate the date of Easter, from astronomical observations on the Vernal Equinox.

In A.D. 725, an English monk, the Venerable Bede (later known as Saint Bede), made the general rule for determining the date of Easter, by stating, “The Sunday following the full Moon which falls on or after the equinox will give the lawful Easter.” However, the Ecclesiastical rules are more specific.

Easter was determined to occur on the first Sunday, after the Ecclesiastical or Paschal Full Moon (actually determined to be the 14^th day of an Ecclesiastical Lunar Month, determined by the Ecclesiastical New Moon. This date could be a couple days away from the actual, astronomical Full Moon.), which occurs on or soonest after the Vernal Equinox (which is fixed as March 21, even if this Spring Equinox occurs on March 19 or 20, which often happens).

The Ecclesiastical Lunar Month is defined as having only 29 or 30 days (relative to the Sun, the Moon orbits the Earth in about 29.53 days, known as the Synodic Month). Consequently, a Lunar Year of 12 Lunar Months has only 354 days, far shorter than the traditional Solar Year which has 365 days (366 days during a Leap-Year). When the difference in the Ecclesiastical Lunar Year and the Solar Year reaches or exceeds 30 days, then an additional Lunar Month is added to the Ecclesiastical Lunar Year!

One of the reasons the date for Easter varies is due to the use of the Gregorian Calendar, a reform introduced by the Roman Catholic Pope Gregory XIII in 1582. By the Gregorian Calendar, Easter always falls between March 22 and April 25, within about seven days of the actual, astronomical Full Moon. The most common date for Easter, in the Gregorian Calendar, is April 19.

Orthodox or Eastern Catholic churches often do not celebrate Easter the same week as traditional Christians; sometimes the two festivals are a few weeks apart. However, occasionally the Orthodox Holy Week does coincide with the Traditional Holy Week.

Orthodox churches continue to use the Julian Calendar to calculate Easter and other feast days including Christmas Day (January 7). By the Julian Calendar, the March 21 date of the Equinox is equated with April 3 (in our current century), when converted to the Gregorian Calendar used as the civil calendar of all nations where the Orthodox Christianity is predominant. Then, Easter always falls between April 4 and May 8 of the Gregorian Calendar. The Julian Calendar Full Moon is always several days after the actual, astronomical Full Moon, hence, the Orthodox Easter is often later, relative to the visible Moon phases, than the Western Easter.

With the English Reformation between 1532 and 1537, England and English colonies did not comply with the Gregorian calendar reform of 1582, thus remaining with the Julian Calendar. The British Empire did not accept the Gregorian Calendar until 1752. Hence, George Washington was born on February 11 in 1731 by the "Old System" (Julian Calendar), but his birthday is now celebrated on February 22 by the Gregorian Calendar (also, George Washington is now considered to have been born in the year 1732; in the "Old System" calendar, the year 1732 did not begin until March 25).

As reported in SpaceWatchtower on Sunday, 2016 March 27 (Internet link to this report near the end of this blog-post), there has been an effort for many years to fix the actual date of Easter, so Easter would no longer be a movable feast and calculating the date of Easter would be simplified. Since the 2016 report, progress has been limited in the effort to fix the date for Easter.

In November, the Catholic News Agency reported that the Roman Catholic Church and the Eastern Orthodox Church have agreed that the two denominations should celebrate Easter on a common date. Their goal is to come to a common date for Easter in 2025, which would be the 1,700th anniversary of the First Ecumenical Council of Nicea.

One possible obstacle could be tensions between different churches. After Patriarch Bartholomew confirmed in 2018 that the Ecumenical Patriarchate of Constantinople would recognize the independence of the Orthodox Church of Ukraine, the Russian Orthodox Church severed ties with the Patriarchate.

If the date of Easter is ever fixed, Astronomy will no longer be part of this particular determination. But of course, even if Easter is designated as a certain Sunday in March or April, Astronomy will still be needed for the determination of the civil calendar for the actual date Easter falls on each year.

Due to the need to use Astronomy to calculate the date of Easter and other moveable feasts, the Roman Catholic Church has supported an astronomical observatory for several centuries. The Vatican Observatory, originally established as the Observatory of the Roman College of Rome in 1774, is now located in Castel Gandolfo, Italy. The Holy See, since 1993, also operates the Vatican Advanced Technology Telescope at the Mount Graham International Observatory in southeastern Arizona.

In the 1930s and 1940s, a planetarium sky show explaining how Astronomy helped to calculate the date of Easter was shown to the public at several of the early planetaria, including Pittsburgh's original Buhl Planetarium and Institute of Popular Science.

Internet Links to Additional Information ---

U.S. Naval Observatory Web-Site for Computing Local Sunrise & Sunset Times [For locations outside of the United States and its territories, use geographic coordinates (Latitude & Longitude)]:

Link >>> https://aa.usno.navy.mil/data/RS_OneDay

Passover: Link >>> https://en.wikipedia.org/wiki/Passover

Lent Season: Link >>> https://en.wikipedia.org/wiki/Lent

Easter: Link >>> https://en.wikipedia.org/wiki/Easter

Hebrew Calendar: Link >>> https://en.wikipedia.org/wiki/Hebrew_calendar

Julian Calendar: Link >>> https://en.wikipedia.org/wiki/Julian_calendar

Gregorian Calendar: Link >>> https://en.wikipedia.org/wiki/Gregorian_calendar

Hypatia of Alexandria, Egypt -

Link 1 >>> https://www.change.org/p/canada-s-parliament-commemorating-the-first-female-astronomer-hypatia-of-alexandria

Link 2 >>> https://en.wikipedia.org/wiki/Hypatia

Wimmer, A.C., Catholic News Agency. "Why Catholics and Orthodox might once again celebrate Easter on the same date." 2022 Nov. 18.

Link >>> https://www.catholicnewsagency.com/news/252851/why-catholics-and-orthodox-might-once-again-celebrate-easter-on-the-same-date