This came up on the
Adventurers League forums for the new organized play program. According to an admin, Greg Marks, the year for the start of the organized play program is 1489 DR. I put together the following from various sources (often the FR Wiki):
Timeline:
1357 DR - First Grey Box FR setting
1358 DR - Time of Troubles
1367 DR - Second Edition's FR boxed set
1372 DR - Start of 3rd Edition
1376 DR - roughly the end of 3E
1385 DR - Year of Blue Fire, when Spellplague begins.
1479 DR - Year of the Ageless one, main year covered by 4E play. Mystra returns at the end, causing the end of the Spellplague.
1484 DR - The Sundering then takes place. The first novel starts in 1484 DR.
1489 DR - Adventurers League campaign begins.