Today my MacBook Air is one year old. That's not exactly an officially recognized holiday, but it does mean one thing very cool:
I have one year of data on my laptop battery, recorded every 1 minute of computer usage!Epic
A little backstory: I started occasionally keeping track of my laptop's battery several computers ago. Near the end of my previous computer's life I realized I could automate this collection of data. By keeping a record of the battery charge every minute my computer is being used, I am able to track the health of my notebook, as well as study my own computer usage in remarkable detail.

Without further ado, here is what 1 year (152,411 samples) of battery capacity data looks like for my 2012 MacBook Air: