There's a little difference between the two. Something 'historic' is something important or famous in the past. "The first landing on the moon was an historic event" (This event was important or famous.) Something 'historical' is something that happened in the past, or it related to the past (but not necessarily famous). If you used 'historical' instead' of 'historic' for the 1st example and said "The first land landing on the moon was historical', you are NOT saying it was famous, you are just saying it's an event that belonged or happened in the past.