15 Minute Timer

The quarter hour

Fifteen minutes is 900 seconds, four to the hour and 96 to the day. It is the only common block that leaves the minute hand at a right angle to where it started, ninety degrees round the dial, which is exactly why clocks are read in quarters: quarter past, half past, quarter to. Everything else about the fifteen-minute habit follows from that reading.

Why so much is measured in fifteens

• Timesheets. Firms that do not use the six-minute unit bill in quarter hours, logged as 0.25. The tenth-of-an-hour version is on the 6 minute timer.
• Calendars. Scheduling apps snap to fifteen-minute slots by default, so meetings arrive as 15, 30, 45 or 60 and almost never as anything else.
• Appointment books. Parking meters, court listings and booking systems all step in quarter hours because they have to add up to whole hours.
• Named after the walk. The fifteen-minute city is a planning idea measured by how far you can walk or cycle, not by a countdown.

Fifteen as a working block

A quarter hour is long enough to finish something small and short enough to start without an argument with yourself. Two runs make half an hour and four make an hour. If fifteen is more than you want to commit to, five and ten divide the hour just as neatly.

Before you rely on it

The count runs against the system clock, so background tabs stay accurate and do not drift. The alarm at the end is less reliable, especially on a phone that sleeps at some point between now and zero. Keep a proper alarm for the cases where missing it matters, such as medication, a timed exam or something in the oven that burns.