Something like this, just off the top of my head:

declare @StartDate datetime,

@EndDate datetime;

select

@StartDate = dateadd(hh, 1,dateadd(dd, datediff(dd, 0, getdate()), 0)),

@EndDate = dateadd(dd, 1, @StartDate);

select ...

from mytable mt

where mt.someeventdatetime >= @StartDate and mt.someeventdatetime < @EndDate;