Big events are *historic*... but everything that happened before this second is *historical.*
Like this: The Beach Boys "Pet Sounds" was a historic re-imagining of what pop music could sound like. Pop and rock music styles are otherwise well defined, and historical examples are everywhere on the radio.
Also, this example: Historically, most people have bought cars using a loan. It was a historic shift when many gave up loans for leases, saving a little money each month in exchange for surrendering accumulated value.
The historic/historical distinction is one you want to get right because the words mean significantly different things: they describe what is notable versus what is common.
Use 'em correctly and your writing gets sharper. More important than that? Your thinking becomes more precise, and that comes out in all you do.