hoy, imperfect or present?
when we are talking about something that is to happen today (hoy) what tense do we use?
2 Answers
When you are talking about something that is to happen (I assume you mean will happen) today sometime later than now, I think you can use either the future (or "ir a" future) or present. Do not accept this as the definitive answer but wait to see what a native Spanish speaker has to say.
Examples: Hoy voy a estudiar inglés. or Hoy estudio inglés. Iré a la biblioteca hoy. or Voy a la biblioteca hoy.
Hello madertracy,
Welcome to the SpanishDict forum 
You asked:
When we are talking about something that is to happen today (hoy) what tense do we use?
I would agree with Jubilado that you could certainly use the immediate or near future as it is called, which uses the ir a construction to talk about (or describe) events that are going to happen shortly.(very soon)
ex: ¿A qué hora vas a llegar a casa, hoy?
= At what time are you going to arrive home, today?
ex: Los niños van a jugar en el parque local esta tarde.
= The children are going to play in the local park this afternoon
You would not use the imperfect to talk about events that are going to happen later today!
The imperfect indicative is used to talk about something that you were doing or habitually used to do on a regular basis:
ex: Íbamos ir la playa para jugar el voleibol todos los sábados põr la mañana cuando éramos niños.
= We used to go to the beach to play Volleyball every Saturday morning when we were children.
Although I also am not a native speaker I am taking regular and frequent Spanish classes with a native speaker from Spai..through Skype. 
I hope this helps
