How should I represent time in OWL in this case?

Hi,

I'm developing an ontology about weather forecast, which will contain some
temporal information. I'm building my ontology based on some existing XML
files, in other words, trying to represent and convert the XML elements to
ontology OWL style. Here is my questions:

in the XML files, there is some elements about time, for example

<SingleDateTime>
  <caldate>20100502</caldate>
   <time>150000</time>
</SingleDateTime>

These elements describe the date and time of the forest. In my ontology,
I'd like to say
myOntology:forecast externalOntology:hasTime externalOntology:timeInstant

Is there some common practice in expressing this statement? I found
ontologies like SWRL temporal ontology and the SWEET (Semantic Web for
Earth and Environmental Terminology) ontology have classes and properties
for temporal expressions, while I'm not sure what's the appropriate
practice in the community. Which existing temporal ontology
classes/properties are more frequently used?

I'd appreciate your suggestions. Thank you for your help!
Miao