Using Present Simple and Present Continuous to Talk about the Future

Present Simple is used when a future event is part of a time-table or a programme.

The meeting starts at 8:00.
The train leaves in 15 minutes.

Present Continuous is used to talk about future arrangements. Some preparation has already happened and there is a suggestion that more than one person is aware of the arrangement.

We‘re leaving on Monday. (We have already bought tickets.)
He‘s meeting her at the cinema tonight. (They agreed to meet.)
Is Anna seeing Jim tomorrow? (Is there an arrangement?)
They aren’t leaving until the end of the month. (There is no such arrangement.)