A calculator inspired by the classic HP-01 calculator watch: • Performs calculations on four datatypes: numeric, elapsed time, time of day, and date. • Find the day of the week, add or subtract days from a calendar date. • Compute percentage, swap inputs, convert an elapsed time to and from decimal time. • Store any type of value in persistent memory. The Watch app provides a subset of these features: • Calculations on all datatypes. • Percentage and memory storage.