Date Wheel 3.01
the author of this app says:
Date Wheel easily calculates the time between two dates with one of the best user interfaces for date calculators.
Date Wheel is the electronic version of the plastic wheel-shaped calendar used by businesses to calculate lead times. It can also be used to calculate the time between two dates or to calculate the Julian date for any day of the year. The time is calculated in months, weeks, days, and business days. This handy program performs all the functions of your plastic wheel and more. New 'today' lock feature makes countdowns automatic! Save tasks for future reference. Use for both business applications and personal applicationsanytime you need to quickly calculate the time between two dates.
Date Wheel supports 5 way navigation. The user interface was designed to fit any user's needs, including being optimized for the Treo. All the screens can be manipulated via a stylus, fingers (using the larger fingertip buttons), 5 way navigation, keyboards, and/or Graffiti.