Alright, I'm a bit of a pedant, so I can't let this little discussion go. Here are a few quotes:
House of Chains, Tor MMPB, p.973-974 said:
Outside stole the first light of dawn.
And Sha'ik reached for her helm.
[...]
There were desert warriors huddled here and there, wrapped in their ochre telabas, spears thrust upright, iron points glistening with dew as the sun's fire broke on the east horizon.
House of Chains, Tor MMPB, p.995 said:
It was past midday. Almost seven bells since the Adjunct cut down Sha'ik.
So Sha'ik confronts Tavore right at dawn. On Seven Cities, that has to be around 06:00, 07:00 our time. We know they use midday and midnight as divisors, so I think noon is a safe approximation for midday. If a bell is around an hour, this puts the time about 14:00, just past midday. If a bell is a half-hour, this is only three and a half hours of time total, which would put the time well before noon, making no sense. So unless the sun doesn't rise until ten o' clock, a bell has to be closer to an hour than a half-hour.
I've found other references to "bells tolling" to announce the time, as well, making the derivation pretty clear.
We sail in and out of Time, then back again. There is only one ship, the captain says. All the ships we hail between the galaxies or suns are this ship.