Timeline

Calendar of Harptos
The  Calendar of Harptos  was the calendar used across most of Faerûn.

It was created by the wizard Harptos of Kaalinth, although most people associate the word "Harptos" with the calendar. It was split into twelve months, each lasting three tendays (or thirty days). There were an additional five days that fell between months, bringing the total number of days in most years to 365.

Months
The names of the months and festivals used in Faerûn were as follows:
 * Hammer ("Deepwinter")
 * Midwinter between Hammer 30 & Alturiak 1
 *  Alturiak  ("The Claw of Winter" or "The Claws of the Cold")
 *  Ches  ("The Claw of Sunsets")
 * Spring Equinox on Ches 19
 *  Tarsakh  ("The Claw of Storms")
 * Greengrass between Tarsakh 30 & Mirtul 1
 *  Mirtul  ("The Melting")
 *  Kythorn  ("The Time of Flowers")
 * Summer Solstice on Kythorn 20
 *  Flamerule  ("Summertide")
 * Midsummer between Flamerule 30 & Eleasias 1
 * Shieldmeet occurs the day after Midsummer, once every four years
 *  Eleasis  ("Highsun")
 *  Eleint  ("The Fading")
 * Autumn Equinox on Eleint 21
 * Highharvestide between Eleint 30 & Marpenoth 1
 *  Marpenoth  ("Leaffall")
 *  Uktar  ("The Rotting")
 * Feast of the Moon between Uktar 30 & Nightal 1
 *  Nightal  ("The Drawing Down")
 * Winter Solstice on Nightal 20

1480 DR
In the 1480s DR the Phandazzilers defeated of the Dragon Cultists & prevented the Rise of Tiamat ushering in an era of peace.

1570 DR
Up until 1570s the Sword Coast was going through an age of prosperity. But corruption has slowly leaked into many of the institutional factions across the Sword Coast. Examples include: Many external & internal forces threaten the balance of that power.
 * The Arcane Brotherhood in Luskan slowly slipping into an authoritarian organization attempting to control the flow of Magical objects along the Coast
 * Lord  Dagult Neverember  embezzling half a million Dragons (Gold Pieces) in Waterdeep. After being exiled from Waterdeep he took up residence in Neverwinter helping the lord's there.

1580 DR
In 1581 DR rumblings in the Underdark point to demon lords being allowed access into the Material Plane causing concerns for many factions within the Sword Coast & in the Underdark.

By 1583 DR Waterdeep is in chaos with many criminal factions spilling their bloodshed into the city & the city's oligarchy council seemingly doing nothing about it. The Laws have only become more strict making it hard for most citizens to lead normal or productive lives. The Criminal factions are all looking for a stone that  Dagult Neverember  hid within the city that points the way to his hoard of half a million gold pieces.

On Hammer 20 1583 DR Luskan's precarious relationship between the Arcane Brotherhood & the Red Hexagon Trading Company finally broke out into an explosive confrontation. It is rumoured something occurred that spell-jammed or took away many properties of magic items and the mages themselves. The Red Hexa-gons led a slaughter on the Arcane Brotherhood's university throwing the entire city into chaos. The Red Hexagon Trading Company enacted their own law and order onto the city causing many civilians to flee to the closest neighboring city, Neverwinter.

Neverwinter has become slowly slipping into xenophobic despite it being a multi-racial cosmopolitan, the new lord is skeptical of many of the races in the city. This only becomes exacerbated by the refugee crisis from migrants coming in from Luskan.

Alternative Timelines
The discovery of the ninth school of magic, Chronomancy, in 1480s DR has led to many "ripples" in the timeline. Most have stayed close or true to the Prime timeline. Below is the notable exceptions.

1530 DR
This age was marked by the discovery of the ninth school of magic, Chronomancy entirely by accident in 1480 DR by an adventuring party named the Phandazzilers. The events of this alternative timeline is only written in logs of two scholars of note Nyx & Raham.

It depicts a world where the Rise of Tiamat was not stopped and the Sword Coast became a unified fascist nation state dedicated to please the god Tiamat's desire for wealth and total domination. It reads much like fiction and was promoted that way. The Harpers & Lord's Alliance have confirmed however that it is not fiction.