Here are two ways to retrieve SQL records modified in the last hour. The first method uses a fraction of a julian date to return the last hour. The second method uses the DateAdd function. I prefer using the DateAdd method just because it is easier to read.
Select y.ModDate
from yourtable y
where y.ModDate > GetDate() – 0.04166
OR
Select y.ModDate
from yourtable y
where y.ModDate > DateAdd(minute, -60, getdate())