Spinrdf sp:now function is not returning anything - sparql

Question

SPIN is a way to represent a wide range of business rules.
This is the official one line description for spin (spinrdf).
Spin enables users to represent their rules with sparqls in ontologies.
I needed to make these descriptions since there is no spinrdf tag.
I have been using spin about a week to write some rules. Now I'm writing some functions to simplify my sparqls in my rules. I have a written a simple date comparison function compareDates. When I call the function with the following sparql there is no errors and gives the expected result.
SELECT ?result
WHERE {
BIND(:compareDates("2015-03-03"^^xsd:date, "2015-06-09"^^xsd:date) as ?result)
}
I would like to use sp:now function comes with spin. When I use the following sparql I have no output.
SELECT ?result
WHERE {
BIND(:compareDates("2015-03-03"^^xsd:date, sp:now()) as ?result)
}
Then I tried the following, but no luck:
SELECT ?result
WHERE {
BIND(sp:now() as ?now)
BIND(:compareDates("2015-03-03"^^xsd:date, ?now) as ?result)
}
And then I decided to see what sp:now returns and I have runned the following sparql the result is null. This lead me to a conclusion that I won't be able to run this function.
SELECT ?now
WHERE {
BIND(sp:now() as ?now)
}
I would like to use that function or similar one but I don't get the problem. Any comment is appreciated.
UPDATE 1
As shown in the following screenshot, the function does not contain any body! This would be the problem but, why it's been placed in the related ontology if won't work.

Answer 1

After some research I have find out two alternative methods for having now datetime. In fact there exists a sparql implementaion of now() function documented here.
SELECT ?now
WHERE {
BIND(now() as ?now).
}
This sparql will return the following:
[now]
2015-03-24T22:12:29.183+02:00
There is an alternative method placed in spin ontology; afn:now() which is placed under spl:MiscFunctions class. This function will give the same result.
By the way, I have been using xsd:date as my functions argument but the both now function alternatives returns xsd:dateTime literals.
To convert these to xsd:date is another story.
There exists some cast functions but they convert only type but not trim the hour part of the xsd:dateTime which causes my comparison to fail.
Thus have come up with the following sparql which uses an indirect approach to convert xsd:dateTime to xsd:date :
SELECT ?nowDateTime ?nowDate
WHERE {
BIND(now() as ?nowDateTime).
BIND(spif:cast(spif:dateFormat(?nowDateTime, "yyyy-MM-dd"), xsd:date) as ?nowDate).
}
Which converted the successfully.
This could be a premature way to convert between to date literal types but this is what I have came up to solve my problem.
Any advice is appreciated.