Hi,
Supposing you're running postgresql and start_date and end_date are timestampz datatypes you could split date and time with something like this:
for date:
select start_date::DATE from time_intervals
for time:
select start_date::TIME from time_intervals
You could try a real example with acs_objects table in your oacs instalation: select creation_date::DATE from acs_objects
A good reading about dates and times in postgresql is http://techdocs.postgresql.org/techdocs/faqdatesintervals.php . it is a little outdated but still works :)
