There is a bug in libical's icaltime_compare_date_only routine.
If the dates are stored in different time zones, the comparision becomes
incorrect.  For example, if I'm comparing 9 PM in Eastern Time to 1 AM
UTC, they should be the same date -- but because of the different time
zones, they appear as different days.

The answer is to convert both dates into the same time zone.
The addition of a 'tz' parameter allows the time zone to be selected,
at the expense of requiring all calls to the function to have a parameter
added.  If passed in as NULL, then UTC zone is used.

I apologize for presenting this in this rather stupid manner, but I
can't/don't want to figure out freshmeat to create a bug report or patch.



/** 
 *      like icaltime_compare, but only use the date parts.
 */ 

int
icaltime_compare_date_only(const struct icaltimetype a_in, const struct icaltimetype b_in, const icaltimezone *tz)
{
    int retval; 
    struct icaltimetype a, b;

    /* We may need to select a time zone to compare, to avoid
       stupidity where 9 PM Saturday matches Sunday because we're in
       America, which is a couple hours off from UTC,
       and such similar stupidity.
    */
    a = icaltime_convert_to_zone(a_in,
                 tz == 0 ? icaltimezone_get_utc_timezone() : tz);
    b = icaltime_convert_to_zone(b_in, tz == 0 ? icaltimezone_get_utc_timezone() : tz);