I have yet to figure out a system, I'm thinking of getting some magnetic tags
Around the top shoulder of my 5 gallon cans, I wrote the numbers 1 through 12 in permanent marker. I then place a tiny neodymium dot magnet on the can indicating the month filled.
Based on the advice I gave above (regarding winter blend), anything filled up between September 15th and the end of May goes into my cars ASAP, since I don't want to store that for more than a few months, and certainly not over the summer months.
Really though, I try not to fill more than one 5 gallon can at a time. The rest I hold onto empty until needed. I have 50 gallons worth of 5 gallon steel cans, plus another 25 or so gallons I could store in plastic and smaller gas cans.
However, only a large regional weather event would be cause for me needing to stock up, and such events do not appear out of thin air. I have never heard of an Atlantic hurricane in my lifetime where I wouldn't have at least a week's worth of notice. If I'm in or near the 7 day cone, I'll get 10 or 15 gallons. Once I'm in the 3 day cone, I'll fill up. That's still 48 hours before the gas stations get packed with late comers.