It requires you to fill in a date & time of arrival and your travel time. When to Leave? then gives back a time & date on which you need to leave in order to make it on time. You can also calculate the time it will likely take to travel a given distance, based on configurable average speeds, for walking, running and cycling.
The app also supports a number of different colourful themes, to match your preference and notifications to remind to get going.

For any issues, you can contact me on my e-mail.