986 AD (summer): Icelandic trader Bjarni Herjolfsson and his crew are driven off course by bad weather on their way from Iceland to meet Bjarni's father at the new Viking colony in Greenland. While they are lost off course, they sight Labrador (Markland, or Forestland, Woodland) south of the medieval treeline near present day Nain. They don't go ashore while they are lost. Eventually they ride a southwest wind back to the Eastern Greenland settlement at Herjolfsnes (Ikigait), Greenland. Bjarni gives up trading and settles at Herjolfsnes to live and farm with his father. Following the death of Norwegian King Olaf Tryggvason in 1000 AD, Bjarni travels to Norway and tells Earl Eirik of his discovery of Labrador. (1)
Land west of Greenland was probably not unknown around 986 AD. Eirik the Red had explored the west coast of Greenland for three years between 982 and 985. The 2000 metre (6100 feet) high mountains behind the Greenland Viking colonies were climbed (2), and the simple eye-to-horizon formula ~3.9 x the square root of the observer's height above sea level in metres = the distance to the horizon in kilometres, shows us that it is possible to see from the highest coastal mountains of Greenland, on a clear day at least, the cloud formations associated with the coastal mountains of Baffin Island (Helluland), if not the highest peaks of Baffin Island itself.
As an example, it is 377 kms from Greenland to Cape Dyer, Baffin Island. The highest mapped point of land on Greenland near the coast is about 2180 metres above sea level. From this point of land, an observer can see roughly 182 kms, or just under half way across the Davis Strait to Baffin Island. On Baffin Island, mountain peaks are somewhat higher, although exact elevations haven't been mapped. Thus, adding the results of both eye to horizon calculations together, it might indeed be possible to see Baffin Island from Greenland on an exceptionally clear day (just as it is possible to see Cape Breton Island from Table Mountain near Port aux Basques, Newfoundland on a clear day). However, it would most certainly be possible to see the cloud formations that are only associated with land and that were well known to Viking seafarers.
~1000: The climate of northern Europe is warming. Drift ice is rare south of the Arctic Circle. This warm period continues until about the year 1200. (2a) Drastic changes in the Earth's climate can occur within decades. (3)
1000: Iceland becomes Christian.
*****1001 (spring and summer): Bjarni returns to his home in Greenland. Leif Eiriksson (son of Eirik the Red, the chief coloniser of Greenland) buys Bjarni's ship and hires a crew of 35 men. Leif sails west and discovers Baffin Island (Helluland, or Flat Stone Land), Markland and Vinland (northern Newfoundland).(1) [Note: 'discovers', as used here, means 'becomes aware of' or 'reveals' as in 'becomes aware of to themselves' or 'reveals to themselves'].
1001: Leif Eiriksson discovers and names Vinland (present day northern Newfoundland) and settles at Leifsbudir (Leif's Booth). The remains of that Viking settlement are preserved and protected today by the Federal Government of Canada at L'Anse aux Meadows. It remains the only authenticated Viking settlement in North America.
1001-1002 (autumn, winter, spring): Leif Eiriksson and his crew stay in northern Newfoundland at L'Anse aux Meadows.
1002 (spring): Leif Eiriksson and his crew leave L'Anse aux Meadows and return to Greenland. At this time, the Vikings had invaded and conquered much of Europe. Although the lines of communication between Greenland and Europe were thin, word of Leif Eiriksson's discovery spread far and wide and became part of the lore with which future European generations grew up.
1002 (summer): Thorvald Eiriksson, Leif's brother, learns of Leif's exploits and sails with a crew to L'Anse aux Meadows and spends the winter there in peace.
1003 (spring and summer): Thorvald Eiriksson explores Newfoundland's west coast.
1003-1004 (autumn and winter): Thorvald returns and spends another winter at L'Anse aux Meadows.
1004 (summer): Thorvald sails north to Labrador and is killed by an arrow during an exchange with the natives.
1004-1005 (autumn and winter): Thorvald's crew returns and winters at L'Anse aux Meadows.
1005 (spring): Thorvald's crew returns to Greenland with the news of his death.
1005 (summer): Thorstein Eiriksson, Thorvald's brother, sets out for Labrador to retrieve the body of his brother. However foul weather prevents him from making much progress all summer and he returns to Greenland.
1005-1006 (winter): Gudrid, widow of Thorstein Eiriksson, marries Thorfinn Karlsefni.
1006: Thorfinn Karlsefni, a wealthy Norwegian, leads a colonising expedition to Newfoundland with three ships, 160 men (some with their wives) and a bull, along with other livestock. Leif Eiriksson agrees to lend Thorfinn his houses at L'Anse aux Meadows (Leif didn't go with this expedition). The expedition spends a peaceful winter at L'Anse aux Meadows.
1007 (summer): Gudrid, wife of Thorfinn, gives birth to Snorri. Snorri is thus the first known European to be born in Newfoundland. The Viking colonists first meet and trade with the natives.
1007-1008 (winter): A native is killed while trying to steal weapons from Thorfinn. A battle with the natives later ensues.
1009 (spring): The Karlsefni expedition returns to Greenland where they spend the winter.
~1010: Freydis, sister of Leif Eiriksson, and a crew mount a joint expedition with Icelanders Helgi and Finnbogi to L'Anse aux Meadows. The expedition is racked by mistrust and murder.
~1011: Freydis, having murdered the men of Helgi and Finnbogi's crew, returns to Greenland in early summer with the remaining members of the expedition. *****
1028 or 1030: Gudrid, mother of Snorri and the widow of Thorfinn Karlsefni, journeys to Rome on a pilgrimage.(3)