Judah McAuley noted: >>I'm going to be sending information back and forth between two [health care] applications. >>I'm inclined to use an existing microformat for this data exchange if possible Hi Judah, For two offices within the same practice, I would think using something like iCalendar would probably be okay. If there was a need to share information 'outside' the organization; schedule time at a surgery center or a rehab facility for example, then you might want to look into whether the medical community has already defined an EDI signal for sharing calendar information or not. I didn't see anything in a quick look. I saw the usual Purchase Order signals I have a little familiarity with; 850, 855, 856. I saw an 'injured worker 837' link. And I saw something claiming that the X12 format might handle calendar data ... along with some other links disparaging X12. <shrug /> Sooooo, it might be worth taking an hour to ask/look/peek around and see if a medical calendar EDI format exists already ... but only if you think you might need to share the data outside the practice for some reason. HTH, RonL. * Then again, if this data is read in and used by 'packaged software' in one or more of the offices then conforming to an established standard could give them more flexibility in selecting/upgrading their other software in the future.