@JeremyECrawford If I cast Haste, can I take a second action on the very same turn or does it not take effect until next round?

— Skarlman (@BadSkarl) October 9, 2015

Haste takes effect immediately. You can cast it on yourself and take the extra action on the same turn. #DnD https://t.co/0qLICmkAAX

— Jeremy Crawford (@JeremyECrawford) October 14, 2015