Since ~1400: Europeans take up more or less regular trade contact with America / Atlantis. While they only import tobacco first (which isn't smoked in TTL first, but burned and inhaled instead, and mostly used as a medicine), the Europeans soon discover the value of beaver and raccoon pelts. Since the natives (called Atlanteans, what else) don't have much gold, the Europeans aren't too keen on extending their discoveries at the moment, only go as far south as OTL Virginia. At the beginning, the trade is in the hands of the Hanseatic League, which helps the princes of Holstein-Holland-Hennegau to become pretty rich.
1416: Robert of Scotland tries to murder his brother, but his conspiracy is prevented, and he is incarcerated for the rest of his life. (Unfortunately for him, he'll become 80 years old.)
1417: After the death of king Harald IV, his brother governs Denmark until his nephew Erik VIII comes to age. Now however, Holy Roman Emperor Gerhard II (who already owns Jutland as a fief) conspires with the regent's younger brother, eventually taking power in Denmark for himself.
1418: Portugal discovers, claims and later settles the Azores.
1421: France makes a separate peace with the Netherlands, giving emperor Gerhard II Flanders, which is incorporated into the Netherlands. Now, the tides turn again: Storming each and every city, the conquered cities with cannons and relying on their greater manpower, the French slowly drive the allied English and Castillians back.
After the death of Pedro II of Portugal "the Cruel", the country descends into Civil War.
1424: The Cortes, the Castillian estates, protest the high costs and low results of the war. King Pedro is sorry about it, but has to leave the war too. He has better things to do: Interfere in the Portuguese Civil War, where the sons of unpopular king Pedro II fought against each other after his death. At the end, Pedro III of Castille becomes new king of Portugal, and the two sons become princes of North and South Portugal respectively. By using this division, Castillian kings can keep Portugal under control, although they have to respect Portuguese rights.
When the Pope and the Anjou king of Naples asks the French king for a crusade against the Rum-Seljuks, king Charles IV agrees. He makes peace with the English, leaving Guyenne in their hands; king Richard III has to accept it as a fief, though.
1434: Portuguese discoveries (which suffered due to the Civil War) restarted again. At the moment, they have reached Cape Bojador, which is believed to be impassable.
1435: Black Death hits the New World, destroying some small European settlements too; other trade places have to be given up, since the Atlantean trade partners have died or don't want to have contact with the Europeans any more. They now concentrate on a few places: Haraldsland (Newfoundland), New Jutland (Nova Scotia), Prince-Harald-Island (Manhattan), Nieuw Zeeland (Atlantic City island), plus the Scottish-Norwegian colony on Martha's Vineyard.
1438: The kings of Denmark and the Netherlands finally agree for a compromise in the New World, negotiated by the pope: Denmark keeps the northern colonies (Prince-Harald-Island, Haraldsland, New Jutland), which are extended with time over the whole OTL Canadian Maritimes and the Hudson valley. The Netherlands get the Southern colony of Nieuw Zeeland and are allowed to colonize the lands further south.
1439: Brittany gets a pro-French ruler, eventually returning to the fold.
1441: Mayapan destroyed (no Europeans involved).
1449: Portuguese captains manage to sail around Cape Bojador, which was believed to be the last safe point you can sail to. Now they've proven the opposite. The way around Africa is opened.
In Portugal, a revolt against the rule of Castillian king Pedro IV starts.
|Earlier in time:|
Western Europe 1350-1400
|Western Europe / Atlantis
|Later in time:|
Western Europe / Atlantis 1450-1500
|Rest of the world 1350-1400|