It's not really a matter of recalibrating. It's simply a matter of what they call voltage suppression. The phone's meters should have certain tolerances built in that allow for a percentage of voltage suppression before it would assume that it's reached a certain Plateau. Apparently there is not much difference in voltage between 8 percent and 0 and so whatever you had running in the background was sufficient to pull the voltage down and trigger a shutdown.
It may not have been any particular power intensive application, but simply a combination of one or more less intensive ones that happened to perhaps trigger an update at the same time and the combination of the two or more were sufficient to pull the voltage down enough to trigger shut down.
What you can do to prevent that in the future is as you see you're reaching near zero on your phone, make sure you end applications that you're not actively using. On the other hand, if you follow my threads you'll see that I'm an advocate of not pushing your battery levels down below 15% if at all possible. When battery levels are within 15 percent of either 100% full or 0% empty, it stresses the battery and ultimately results in a shortening of its overall life span. It also therefore means that as the lifespan gets shorter, each subsequent charge will last a shorter period of time as well.
These batteries are defined as having reached the end of life when they will no longer hold at least 80 percent of its original rated charge capacity. This means of course, that a 100 percent charge would only result in approximately 80% of the usage time that you would have gotten when the battery was brand new. Therefore, 10% charge remaining would actually feel and act a lot more like 8% (or less) in that example.
These lithium-ion batteries prefer to be recharged partially numerous times throughout the day as opposed to being fully charged and then fully depleted before being recharged again. I recommend you carry a spare charger with you and plug in whenever convenient, or carry a portable battery backup and use that to boost the cell phone's battery power intermittently throughout the day as well.