Two hours is the length of a feature film, a great many written exams, and the stretch of driving after which every road safety body suggests a break. It is also when sunscreen needs reapplying and when a braise starts to give. Long enough to be a commitment, short enough to plan around.

What people use this timer for

Sitting or invigilating a standard written exam
Driving a leg of a journey before stopping to rest properly
Reapplying sunscreen during a day outdoors
Braising tough cuts until the connective tissue softens
Watching a film without pausing halfway through
Using a short-stay parking bay without risking a ticket
Standing up and moving after a long stretch at a desk

For long drives, set the two hours when you pull away, not when you remember. Tiredness builds quietly, and the point of a fixed interval is that it makes the decision to stop before your judgement is the thing being tested.

Questions about this timer

How often should sunscreen be reapplied?

Roughly every two hours of sun exposure, and sooner after swimming, towelling off or heavy sweating. The initial layer is also usually thinner than the amount products are tested with, so generosity matters as much as timing.

Why break every two hours when driving?

Concentration falls away gradually and drivers are poor judges of their own alertness. A planned stop of fifteen minutes or so resets attention before fatigue has a chance to affect reaction time.

Is two hours enough to braise tough meat?

For many cuts it is a good starting point at a low, steady heat, though larger or tougher pieces want longer. The test is whether a fork twists the meat apart easily rather than whether the time is up.