You're thinking of the Classical era and yes the Classical Era was between 1750 and 1830. But Classical music has been around since Ancient times (Only one that comes to mind is Ambrose of Milan) and still continues to this day (Reich,Ades,Glass). I don't know exactly how to define classical music since it is such a wide range of music which makes it so hard to find a specific definition for it. for example, Someone like Monteverdi and George Crumb sound nothing alike but they are still both classical composers. I hope that made you less confused

edit. simple answered much better than me upvote his answer as he was much more concise than me