In Islam, there are some ceremonies and occasions which are held all around the world among Muslims. They all have religious backgrounds and are mostly referred to in the holy Quran. Muslim nations have been commemorating them in the course of history. Here we are going to have a glance at the most significant Islamic occasions based on the Lunar Calendar.

6 Major  Islamic Occasions 

1.10th of Muharram: Martyrdom of Imam Hussain (AS)

The month of Muharram is the first month of the year in the lunar calendar. On the tenth day of this month, Hussain Ibn Ali (AS), the grandson of Prophet Muhammad (PBUH&HP), and his companions were brutally martyred, and their women and children were taken captive by the caliph of the time, Yazid ibn. Muawyah. Their story has been the source of inspiration for many new converts. 

2. 20th of Safar: The Day of Arbaeen

Arbaeen is the Arabic word for forty, and it marks the 20th of Safar, the fortieth day after Imam Hussain's (AS) martyrdom on the day of Ashura, who was martyred in the event of Karbala along with his companions in the cruelest and most inhumane way possible. 

According to some historical accounts [2], some of the members of Imam Hussain's (AS) family after being released from the bondage of Yazid's forces returned to Karbala from Sham (today's Damascus) to visit Imam Hussain's (AS) grave. Also, some believe that Imam Hussain's (AS) head, which was taken to Sham by Yazid's army was brought back to Karbala on this day and buried with his body [3] & [4]. 

Every year, a few days before this day, a vast number of people from all over the world, Muslims or even non-Muslims, gather in Iraq to take part in a symbolic walk, to revive the teachings of Imam Hussain (AS) and commemorate his sacrifice in the way of Allah and humanity. 

3. 17th of Rabi al-Avval: Prophet Muhammad's (PBUH&HP) Birthday

There is a disagreement concerning the exact date of Prophet Muhammad's (PBUH&HP) birthday. Some believe it occurred on the 12th of Rabi al-Avval, while others consider it to be on the 17th of Rabi al-Avval, the third month in the Islamic calendar. Prophet Muhammad (PBUH&HP) was born in Mecca. All Muslims around the world celebrate his birthday and regard it as one of the important Islamic occasions. On this day, Muslims feed the needy, pray and recite the Quran, commemorate Prophet Muhammad (PBUH&HP), and his challenges to deliver the messages of Allah to human beings.

4. 1st of Shawwal: Eid al-Fitr

The first day of the month of Shawwal, the tenth month of the Islamic calendar, is called Eid al-Fitr. After fasting for one month, during the month of Ramadan, remembering, worshipping Allah and trying to do fewer sins beside not eating and drinking from before the Call for Fajr prayer to after the Call for Magrib prayer, Muslims celebrate the first day of the month of Shawwal, for their success in submitting to Allah's command. They perform the Eid prayer first; then, they hold a feast inviting their loved ones, wear their best clothes, and visit their friends and family. The culture of feasting might be different in different Islamic communities, but one thing is for sure; no one is allowed to fast on this exceptional day. Allah also obliges Muslims to share their blessings and happiness with the needy with the money they donate to them. 

5. 10th of Dhu'l-Hijjah: Eid al-Adha

Eid al-Adha is one of the most significant Islamic occasions. Some of the most important events of this Abrahamic religion happened on this day. On this Eid, similar to Eid al-Fitr, Muslims are not allowed to fast. The first is the sacrifice of Ishmael by his father, Abraham, for the sake of Allah. When Abraham and his son both surrendered, and he was ready to behead his son, Allah sent a ram and asked Abraham to kill that instead.

"So when they had both surrendered [to Allah's will], and he had laid him down on his forehead, We called out to him, 'O Abraham! You have indeed fulfilled your vision! Thus indeed do We reward the virtuous! This was indeed a manifest test. Then We ransomed him with a great sacrifice, and left for him a good name in posterity." (37: 103-108)

This day is also the last day of Hajj rituals, in which Muslims shall sacrifice an animal to feed the needy Muslims. On this day, those who attended Hajj have performed all their Hajj rituals, and with the great assistance of Allah, all their sins are wiped away, and Allah accepts their good deeds and repentance.

Many Muslims celebrate this day. They sacrifice an animal to feed the needy, even if they have not attended Hajj. If they do not have enough money to buy a sheep, they do other things and feed the destitute in different ways. This sacrifice is an expression of generosity and obedience to the commands of Allah. This Eid also reminds humankind of the characteristics, such as envy, rage, dishonesty, etc., they have to symbolically sacrifice in themselves to become the better version of themselves and be worthy of being Allah's best creation. 

5. 18th of Dhu'l-Hijjah: Eid al-Ghadir

This Islamic occasion was a day in the last Hajj pilgrimage (Hajjat al-Vida'a) of Prophet Muhammad (PBUH&HP). When he was going back to Medina with all his companions and other pilgrims, he gathered everyone around a place called Ghadir and announced these words in which he appointed Imam Ali b. Abi Talib (AS) as his caliph and the Imam after himself following a direct order from Allah [i]:

"Whomsoever, I am his leader (Mawla), Ali (AS) is also his leader (Mawla). O' Allah! Love those who love him (Ali (AS)) and oppose those who oppose him" [1]

This is another important day in the Muslim calendar. On this day, Muslims can fast and again feed the needy, as an essential part of Islamic culture. 

These are the most significant and most celebrated Islamic occasions. As one can see, feeding others and praying to Allah are the essential things a Muslim should do to celebrate a feast, which reveals the importance of caring for others in Islam that results from the devotion to Allah.  

Notes: 
[i] Verse 67th of Surah al-Maedah known as Al-Tabligh Verse, and the third verse of the same chapter known as Al-Ikmal Verse. 

References:

1.  Ibn Athīr, Usd al-ghāba, vol. 3, p. 605; Kulaynī, al-Kāfī, vol. 1, p. 295; Balādhurī, Ansāb al-ashrāf, vol. 2, p. 110-111;
2.  Ibn Tawus, 'Ali b. Musa, Al-Luhuf 'ala qatla l-tufuf, Uswi, Qom, 1414 AH.
3.  Al-Biruni, Abu Rayhan, The Remaining Signs of Past Centuries, p.331.
4. Qazi al-Tabataii, Muhammad Ali, A Research on the first Arba'een of the Leader of Martyrs (Imam Hussain (AS)), vol.3, p.304.
    

The responsibilities of a Muslim towards family, relatives and other Muslims in general, were already reviewed in an article. Here one's responsibility in Islam towards neighbors, friends, and enemies are discussed.

The Responsibility in Islam Towards Neighbors 

Doing good to neighbors is highly emphasized in Islamic teachings: “Worship Allah and … be good to … the near neighbor and the distant neighbor” (4:36). Prophet Muhammad (PBUH&HP) advised Imam Ali (AS) to honor the neighbors, even if they are disbelievers (Kafir) [1]. Imam Ali (AS) said that Prophet Muhammad (PBUH) used to invite repeatedly to doing good to neighbors such that we thought he (PBUH) was going to consider an inheritance for them [2].

The rights of neighbors on one another as an important responsibility in Islam, are:

To honor them in their presence, and to help and care about them when they are absent [3]. It includes visiting neighbors when they are sick, to assist their funeral, and to offer them your tasty meals that smell good [4];
To keep their secrets. It means that not to look for their faults and errors. And, if ever you become aware of some of their faults, do not reveal them but try to conceal their deficiencies [3];
Do not leave neighbors alone in difficulties [3]; e.g., help them in case of financial needs [4];
Do not be jealous of them if God grants them some blessings [3];
Ignore their errors to yourself and forget about them. If ever they do wrong to you unintentionally, be patient and in peace with them [3];
Do not let others talk behind their back and reveal the deficiencies of your neighbors here and there [3].
Giving priority to the neighbors. It is narrated from Imam Hassan (AS) that Lady Fatima al-Zahra (AS) used to pray firstly for the neighbors and then for members of the family [5]. 

According to Imam Sadiq (AS), having good behavior and interaction with neighbors increases the provision (Rizq) [6]. Prophet Muhammad (PBUH) advised to respect neighbors as much as one should respect his\her mother [6] and he (PBUH) said: “God bless whoever does good to his\her neighbors” [7]. On the contrary, whoever sleeps peacefully at night while one of the his\her neighbors is hungry, God will deprive him of his blessings on the judgment day [8]. The same will happen to whoever annoys his\her neighbors [1]. 

Take your time and think about these attitudes towards the neighbors. Life will be surely much agreeable and peaceful if we improve our social interactions with our neighbors within the Islamic framework.

The Rights of Friends and Companions

Having a good companion is known as a blessing; on the contrary, a bad one is like a disaster [9]. Friends and companions have certain rights one over the other including:

To interact with them with generosity as much as you can, otherwise, be fair to them [3];
To be smiling when you meet them and to receive them modestly [3];
To respect them as they respect you [3];
To be the first one who does good to the other one, otherwise, try to compensate properly [3];
To help them in difficulties and whenever they are in need, as Imam Ali (AS) advised to [10];
To hold them in great affection according to Imam Ali (AS) [11];
Not to reveal their deficiencies and mistakes;
To encourage them in obedience to God and to prevent them from committing sins [3];
To be honest with them and not to cheat [3]; e.g., nor to talk behind their back neither to reveal their deficiencies and to guard their secrets;
To be trustworthy whenever they rely on you [3].

The Responsibility in Islam Towards the Enemies

The enemy here means a person whom one is in conflict with. There are some recommendations in Islamic resources on how to treat enemies and what is one's responsibility in Islam towards them:

To be fair with them [12]. According to Imam Sadiq (AS), a real believer (Mu'min) does not oppress his\her enemies [13];
To testify in favor of the enemies if they are right [14] even if your testimony is against yourself [3];
To keep the promises you made to your enemies [15];
To forgive and tolerate them, if possible [3]. According to Imam Ali (AS), there is a virtue in forgiving enemies [16];
To talk nicely and shortly with whoever you have complained of [3], to argue with them in a way that is best (16:125), and not to ignore their rights if ever you are wrong [3].

References:

1. M. Shoueiri “Jami’ al-Akhbar”, p. 84.
2. Shaykh al-Kulayni, “Al-Kafi”, vol. 7, p. 51.
3. Imam Zayn al-'Abidin (AS), “Treatise On Rights (Risalat al-Huquq)”.
4. responsibility towards others
5. Shaykh al-Saduq, "Ilal Al-Shara'i", p. 181
6. Shaykh al-Kulayni, “Al-Kafi”, vol. 2, p. 666.
7. Shaykh al-Saduq, “Al-Amali”, p. 288.
8. Shaykh al-Kulayni, “Al-Kafi”, vol. 2, p. 668.
9. “Ghurar al-Hikam wa Durar al-Kalim”, T. 4719-4720.
10. “Nahj al Balaqa”, p. 494.
11. “Ghurar al-Hikam wa Durar al-Kalim”, T. 9665.
12. Ibn Shu’bah, “Tuhaf al-Uqul”, p. 88.
13. Shaykh al-Kulayni, “Al-Kafi”, vol. 1, p. 47.
14. Shaykh al-Saduq, “Sifat al-Shia”, p. 24.
15. “Nahj al Balaqa”, p. 53.
16. “Ghurar al-Hikam wa Durar al-Kalim”, p. 435.