Simple present

[cubezero3]

London celebrates St George's Day and Shakespeare's 444th birthday today.

Celebrating St George and the Bard | News

This report was published three days before Shakespeare's actual birth date. The auther used the simple present tense here because the celebration was not taking place on very day and was thus an ongoing matter then. Had the same setence been written and published on April 27th, the writher would have used iscelebrating over celebrates.

Am I right to think so?

[PROESL]

Celebrating St George and the Bard | News

This report was published three days before Shakespeare's actual birth date. The auther used the simple present tense here because the celebration was not taking place on very day and was thus an ongoing matter then. Had the same setence been written and published on April 27th, the writher would have used is celebrating over celebrates.

Am I right to think so?

The simple present is used here because it's a headline, or a "sub-headline" of a news story. This is how most, or many, headlines are written. The headline says "today".

In regular conversation, we would expect to hear "is celebrating", which is the present progressive, of course.