For an indictable offence, there is no time limitation as to when the alleged offence occurred. It could have been historically years earlier. For a summary conviction, or a hybrid offence that allows for the possibility of a summary election, it would have to be six months since the date of the alleged offence. I should back up and say that, for a hybrid offence, the crown has the power to decide whether to prosecute by way of summary conviction or by indictment. A straight indictable offence is just simply that; it's indictable. The other limitation on a summary conviction offence is that the maximum sentence is 18 months, and that's only for a prescribed few offences.
Procedurally, there are other limitations with summary conviction offences, in that they are tried in the provincial court. In Ontario, it would be the Ontario Court of Justice, and there's no right to elect a judge and jury trial.
With some exceptions, for indictable offences there is a right to elect the mode of trial with a preliminary inquiry or a trial by judge and jury. Of course, there are exceptions in the law, but those are the broad differences between a hybrid offence, which allows a choice, and a straight indictable offence.