Have a look at these sentences:
To express that you have done something for + [duration] - i.e. to talk about an action or event that started in the past but is still ongoing in the present - in Spanish you use El Presente with desde hace + [duration] as such:
No he fumado fumo desde hace un año.
Desde + [specific date] = since + [specific date]
In the same context, you will use desde instead of desde hace when your action's starting point is a specific date:
- Use "hace" for "ago" with El Pretérito Indefinido
- Using Hace + length of time + que + present tense to say how long one has done something for