Windows software to convert between Julian, Gregorian, Dee and Dee-Cecil calendar dates in various formats, and to add and subtract a number of days, weeks, months and years to or from a given date. Also displays a sequence of Gregorian and Dee (or Dee-Cecil) dates for up to 800 consecutive days, and dates and times of vernal equinoxes in the Gregorian and Dee(-Cecil) calendars for up to 800 consecutive years. Times of vernal equinoxes may be calculated on the basis either of mean solar time or apparent solar time.