Well, as I understand it, the Hebrew word for "day" meant a 24 hour day. Also the day and night designations did not need the presence of a sun, as there was light before the sun. Probably not from stars though, as they seem to have been created on day 4.
But even the light itself isn't created until verse 3. And no specific time period, day or otherwise, is given until verse 2. I really can't see the time span of verses 1 and 2 being within one 24-hour period. But since days and nights didn't exist until light was created, there really is no such thing as "time" at the very beginning so what goes on before that is probably ageless.