Contrary to popular thinking, the sun does not always exactly rise in the east and set exactly in the west, so much as easterly and westerly positions. Predicting those exact positions is the root of the problem.

One answer comes in the form of the Photographer's Sun Compass, which gives all sunrise and sunset positions throughout the year.

How does it work?

Simply line the compass with the North. The months of the year are indicated on the base and you can see where the sun rises and sets.

Photographer's Sun Compass
For photographers we make 2 versions. The only difference is the display is optimised to different latitude bands for ease of use in the area where you are mainly based

There is a simple to use data table that allows the compass to predict the Sunrise/set positions anywhere on Earth between 60 degrees North down to 50 degrees South.

45-55 degree Version

The instructions and month indicators on the compass side of the unit are optimised around latitude 50 degrees, i.e. London England, but are usable for all areas around the World between latitudes 45 degrees and 55 degrees.

30 - 40 degree Version

This version is optimised for latitudes 30 - 40 degrees. This version is used in the USA, the Mediterranean, South Africa and Austraila etc.
Both Sun compasses work in the Northern and Southern hemisheres. Understandably many clients have difficulty understanding how. 

The fact is, that whilst the distance, for example from London UK  at 50 degrees North down to Cape Town 34 degrees South is 6000 miles, the distance from the Earth to the Sun is 94 million miles. So there is an angular error but it is miniscule. The only difference is the Sun's arc passes through the North in the Southern hemishere and vice versa.

Are the Aps for Smartphones better ?  Undoubtedly yes, but only in locations where you have a phone signal !

Below is the difference between what you planned to shoot and what you may actually get in mid summer.