This online calculator computes travel duration given departure time and city and arrival time and city using time zones information.
Timezone information and a list of cities are taken from the Cities Handbook. Registered users can add new cities to the handbook, and they will appear there after 24 hours.
Please note the DST (daylight saving changes) issue if a city has a different time zone for summertime. By default, the calculator tries to pick up the correct time zone considering the most frequently used dates for the time change: the last Sunday of March and the last Sunday of October. However, this is not always true for some countries. So, if your arrival and departure times are close to the time change date for particular countries, the calculator can be wrong by an hour. In such cases, it is better to calculate results by hand.
This calculator first computes the time difference between selected cities, like in City Timezone Converter, then adds or subtracts this difference to the difference between arrival and departure time. If the result is negative, you should go back in time; in other words, arrival time has already passed in the arrival city.