Present

The present tense can express the present, the future and the past

The present tense is only seldom used to refer to past facts.

Reference to the present

The present tense is used to describe an event that occurs in the present time.

It is possible that the event has begun at an earlier time in the past and is ongoing up until now.

Reference to the future

The present tense is used to describe an event that has not yet begun. In this case, it should be accompanied by a temporal adverbial that will clearly indicate that it refers to a future event.

The present tense with a reference to the future can be used interchangeably with the simple future (Future I) without any semantic difference. Compared to the simple future, the present tense expresses a higher level of certainty regarding the realization of the future event.

Reference to the past

The present tense can also refer to a past event which has already occured. In this case, it should be accompanied by a temporal adverbial, which will clearly indicate that it refers to a past event. It is often used in headlines* or historical lists**. 

The present tense with reference to the past is used instead of the Präteritum; it is, however, more vivid than the Präteritum. That is why it is particularly used in literature.

Note:

The present tense can also be used to describe or refer to universal facts or facts that will always be valid.