The default: the clock starts on the date of injury
Under A.R.S. § 12-542, Arizona's ordinary two-year deadline for personal injury claims generally begins running on the date the underlying incident happens — not the date a claim is reported to an insurer, not the date settlement talks begin, and not the date a lawyer is finally hired. This is the default rule for the overwhelming majority of Arizona injury cases.
When the injury or its cause isn't obvious
Arizona's discovery rule exists specifically for cases where an injury, or the cause of an injury, genuinely isn't apparent at the time it occurs. Rather than starting the clock on a date the injured person had no practical way of knowing mattered, the deadline instead starts running from the date the injury (or its cause) was actually discovered, or reasonably should have been discovered through ordinary diligence. This matters most for injuries that develop gradually, or where the link between an injury and its underlying cause only becomes apparent well after the fact.
Minors: the clock waits for adulthood
Under A.R.S. § 12-502, Arizona specifically tolls — pauses — the two-year clock for anyone injured as a minor, until that person turns 18. In practical terms, a child injured at age 10 has until their 20th birthday to file, rather than a clock that would otherwise have expired years before they were ever in a legal position to pursue the claim themselves.
Mental incapacity: the same protection extends further
The same statutory provision extends this protection to anyone who was "of unsound mind" at the time of the injury. For that person, the two-year clock doesn't begin running until they regain proper mental capacity — recognizing that someone genuinely unable to understand or act on their legal rights shouldn't lose those rights to a deadline they had no real ability to meet.
Two distinct doctrines, not one combined rule
It's worth understanding that Arizona's discovery rule and its minority/incapacity tolling address genuinely different problems. The discovery rule is about when an injury became knowable; minority and incapacity tolling are about whether the claimant was legally capable of acting at all during that period. Whether and how these two concepts interact in any specific case depends heavily on its particular facts, which is exactly the kind of question worth confirming directly with an attorney rather than assuming a general rule applies cleanly.
What doesn't pause the clock
A genuinely common and costly misunderstanding: actively negotiating a settlement with an insurance company does not toll or pause Arizona's filing deadline in any way. The two-year clock keeps running the entire time talks are ongoing, discovery rule or tolling provision notwithstanding.