This article claims to have pinned down the date of Joseph Smith's supposed First Vision.

It hinges on the account of an axe stuck in a stump. Read it and ask the same question I did:

Is there any other reason for chopping wood in 1820 in March in upper New York state?  Like– for a fireplace? For cooking food? Fence repair?

For more information, see The Mormon Mirage 3rd Edition:  A Former Member Looks at the Mormon Church Today(Zondervan, 2009). Also available as an audiobook and as an expanded-text E-book for Nook, Kindle and other reading devices.