For Muslims, the month of Ramadan is a time to reread the Koran, focus one's faith, be charitable and commune with family and friends in celebration of life and God.
The belief is that acts of piety, or even everyday kindnesses, are rewarded even more generously by the Almighty during Ramadan.
Terrorists, particularly members of Isis (Islamic State), espouse a heinous ideology in which such acts of piety include the murder of those they consider infidels. To kill and martyr oneself during Ramadan is encouraged by such extremists.
The collision of Islam's peaceful and joyous Ramadan traditions with terrorists' warped version of them produces a unique kind of dissonance and heartbreak. Most of the victims of Islamist terrorists are other Muslims, after all.
For instance, Isis has bombed a popular shopping street in Baghdad on Ramadan two years in a row. Last year's attack was the worst Baghdad had seen, with more than 300 people either blown up or dead in a fire that subsequently swept through a shopping arcade. This week, 17 people were killed and more than 30 were injured at an ice-cream parlor where families were enjoying dessert after a day of fasting.
Most Muslims fast from sunup to sundown during Ramadan. Dozens more were killed or wounded hours later in front of the Government's main pension office. Isis asserted responsibility for both bombings, saying they targeted Iraq's Shia majority. The Sunni militant group views Shias as apostates.
There is little data to suggest that attacks are more common or more deadly during Ramadan, and in most cases it is hard to draw a clear line connecting an attack's motives and its timing. But Isis leaders certainly make that link in their propaganda.
Two weeks before Ramadan in 2016, a spokesman for the group exhorted followers "to make it a month of calamity everywhere for non-believers". He had issued a similar call the year before.
The months of Ramadan in 2015 and 2016 were filled with Isis attacks. On one day alone - June 26, 2015 - more than 400 were killed in Syria, Somalia, Tunisia, Kuwait and France. Last year, a nightclub in Orlando, Istanbul's airport and a bakery frequented by foreigners in the Bangladeshi capital were among those targeted by extremists during Ramadan. This year, Ramadan lasts until June 24.
Isis fighters are known to invoke an ancient battle fought by the Prophet Muhammad and his followers during Ramadan in the year 624 as justification for their militarised interpretation of the holy month.
The Battle of Badr, fought against non-Muslim Arab tribesmen, was pivotal to early Muslim history. A severely outnumbered Muhammad triumphed and went on to spread his religion. Modern-day extremists who believe themselves to be Muhammad's true followers perceive a parallel battle and expect God to grant similar victories, especially during Ramadan.
But many analysts say the Ramadan attacks of terrorist organisations are an increasingly desperate attempt to project strength in the face of battlefield losses.
Last year, Isis lost control of the Iraqi city of Fallujah during Ramadan, for instance, but still broadcast its capacity for terrorism by carrying out attacks around the world.
If yesterday's attack in Kabul is any indication, the perversion of Ramadan by such militant outfits will haunt us for years to come.