I would argue that 2 days and 1 hour is not a "number of seconds (or minutes, hours, days or weeks)"
If you say something will happen in three days, that's a big time window.
If you say something will happen in three days, that's a big time window.
Calculating the calendar date for an event that’s 365 days in the future needs to consider whether leap-time corrections need to be made during the period. We do that already for days with our standard calendar.
Edited.
Really, I don't think you can reduce any of these to a specific number of seconds. If someone says an event is in 14 hours, the meaning is a lot closer to 14±½ * 3600 than it is to 14 * 3600.