The Movable Type calendar currently features an option to have the current day highlighted by use of the MTCalendarIfToday tag. But this tag is not dynamic, it only refreshes the information on the rebuild of your calendar template. If you'd like this to work automatically with php to autodetect the date (within the same month), I put together a tutorial with code to copy and paste. Movable Type: Calendar using PHP to autodetect date. Hope this helps someone, its been an oft-requested option on the MTForums!