Learn Dutch: Het team vergeet de datum door te geven. - The team is forgetting to pass on the date.

doorgeven is a separable verb. When you use a separable verb in a te + infinitive clause, the te wedges itself between the prefix (door) and the verb (geven). Notice that it is written as three separate words: door te geven.

Why does de datum come before door te geven?

In Dutch, the te + infinitive phrase gets pushed to the very end of the clause. The object receiving that action, which is de datum (the date), must come before it.

I learned that door means 'through'. Why is it used here?

You are right that door usually means 'through' on its own. But here it is the prefix of the separable verb doorgeven. In this verb, door implies passing information or an object 'on' or 'forward' to someone else.

Why is the verb just vergeet for het team? Shouldn't it have an extra 't'?

Het team is a singular subject, so it takes the standard 'stem + t' conjugation. The stem of vergeten is vergeet. Because the stem already ends in a 't', Dutch spelling rules say we don't add a second one.