IRS Cap Gains Excluisonn Dates

[Chris S.]

I have a two family home I purchased in 2006 that was my primary residence up until 2014 when my wife and I purchased a single family.  We are considering selling multi family and I'm aware of tax exclusions on half of home.  Question --is the five year mark calculated with any precision?  Does IRS use exact purchase date of single family in this scenario or is there any wiggle room?  In our situation we didn't move in until a month or two after the purchase.  Any clarity would be a huge help.  Thanks!