SQL query works with variable but not with literal

I have a user-defined table-valued function in SQL Server with name dbo.GetBillsByDate that accepts one date parameter @dateOf.

The function returns successfully for all dates in October of 2015 except for 2015 October 14. The exceptional date causes a divide by zero error and also returns a warning. Here is the exact text:

Divide by zero error encountered.
Warning: Null value is eliminated by an aggregate or other SET operation.

That the function runs on every date besides the 14th is confusing to me, but I've found that when I use a variable to pass in the data the function will return successfully. This causes more confusion.

So:

select * from GetBillsByDate('10/14/2015');

returns an error, and:

declare @dateOf date;
set @dateOf = '10/14/2015';
select * from GetBillsByDate(@dateOf);

does not.

Any insight?

Edit: Full body of dbo.GetBillsByDate

create function [dbo].[GetBillsByDate](@dateOf date)
returns table as
return
select propertyID                              PropertyCode, 
       billDate                                DateOf, 
       accountNum                              AccountNumber, 
       address1                                Address1, 
       address2                                Address2,
       dateadd(day, 1-day(@dateOf), @dateOf)   DatePosted,
       glcode                                  LedgerCode, 
       currMonthPostTotal                      AmountPosted

from AccruedBills

where convert(date, dateCreated) = @dateOf 
      and 
      startDate < endDate 
      and 
      billTotal >= 0 
      and 
      currMonthPostTotal<>0
union
select propertyID, 
       billDate, 
       accountNum, 
       address1, 
       address2, 
       dateadd(day, 1, dateadd(month, -1, dateadd(day, 1-day(@dateOf), @dateOf))),
       glcode, 
       prevMonthPostTotal

from AccruedBills

where convert(date, dateCreated) = @dateOf
      and
      prevMonthPostTotal<>0 
      and 
      startDate < endDate 
      and 
      billTotal >= 0
union
select propertyID, 
       billDate, 
       accountNum, 
       address1, 
       address2, 
       dateadd(day, 1, dateadd(month, -1, dateadd(day, 1, dateadd(month, -1, dateadd(day, 1-day(@dateOf), @dateOf))))),
       glcode, 
       remaMonthPostTotal

from AccruedBills

where convert(date, dateCreated) = @dateOf
      and
      remaMonthPostTotal<>0 
      and 
      startDate < endDate 
      and 
      billTotal >= 0

AccruedBills is a view. The query:

select * from AccruedBills where convert(date, dateCreated) = '20151014'

returns successfully.