I am saying that you shouldn't use day as a unit of time. You should use second, minute, hour, etc, because these have a constant duration. sleep(86400) should reliably make your thread sleep for at least 24 hours.
It depends on the context and the system you’re working with. In some systems, an hour may last 3599, 3600 or 3601 seconds (due to the leap second), a minute may be 59,60 or 61 seconds. Even a second is not always a „true” second.
There’s no single time unit that works for all situations.
There’s no single time unit that works for all situations.