It's really 24+. It's the first half-cycle after 24 hours has passed.
So, if your cycles tend to run at 15 minutes past the hour:
- A trade accepted at 3:10pm will not be finalized until around 3:15pm the following day (around 24 hours)
- A trade accepted at 3:20pm will not be finalized until around 7:15pm the following day (around 28 hours)