The most common format for event data seems to be iCal, but that has the disadvantage of being none too pleasant to parse. There's an RDF schema based on iCal which suffers the same conceptual problems as iCal, but with the added advantage/disadvantage of RDF syntax, depending on who you talk to (I'm firmly in the pro-RDF camp, and even I think that RDF-calendar is a bit awkward). Failing that, there are the microformats such as hCal, which again is essentially another syntax for iCal, but one which has been shoehorned into XHTML.
The most common format for event data seems to be iCal, but that has the disadvantage of being none too pleasant to parse. There's an RDF schema based on iCal which suffers the same conceptual problems as iCal, but with the added advantage/disadvantage of RDF syntax, depending on who you talk to (I'm firmly in the pro-RDF camp, and even I think that RDF-calendar is a bit awkward). Failing that, there are the microformats such as hCal, which again is essentially another syntax for iCal, but one which has been shoehorned into XHTML.