catnap uses a monotonic stopwatch, so changes to the system wall clock do not
alter the requested wait. Progress is written to standard error; standard
output stays empty.
The progress interval depends on the full requested duration:
- Durations greater than one minute report every thirty seconds.
- Durations of one minute or less report every five seconds.
- Durations of twenty seconds or less report every second.
Remaining time is formatted for the current environment locale where a translation is available, with English used as the fallback locale.