Tabi Calc is a calculator specifically designed for travelers. *Tabi is Japanese for travels.
Arrival time - Departure time = Travel time
Timezones support (City names and 3-digit Airport codes)
Automatically detect GPS and set your local currency.
Easy conversion between local and your home currency (iPhone & Apple Watch)
It also works as a regular calculator:
Arithmetic between two numbers
M+, M- buttons
Time difference between two photos
Memory is fixed so that it can hold data after the app quits.
Apple Watch can obtain currency codes by tapping FX button when coming back online.