A couple additions
I was not able to find information on the uses per day, but to extrapolate from the below:
A specific time is required to reset a 'per day' allotment. That time is either set {divine} or limited {needs 8 hrs rest before hand}. Both limit regaining uses during the last 8 hours.
As magic items don't 'rest', I would suggest they fall into the set time category. Items reset time could be set at creation. Dawn, signifying rebirth, new starts, and all sorts of related stuff, would be a good 'normal' time for items to reset.
Ability reset times should be at some meterologicaly identifiable event. Midnight it not obvious by observation. Dawn would be, IMHO, a better choice.
Both items and abilities per day would be limited by the 8 hour clause.
I would go with this as its using the same mechanics for similar uses, and you dont have to track every use throught the entire day. It also makes for a bit more of a planning problem.
Interesting side note.. I learned something! Divine casters dont need 8 hours of 'rest', but only need to stop each day at the proper time. Cool. I can envision issues in my group {2 Druids, 2 Ranger} if they select different times for thier meditation and prayer
SRD Divine Casting said:
A divine spellcaster chooses and prepares spells ahead of time, just as a wizard does. However, a divine spellcaster does not require a period of rest to prepare spells. Instead, the character chooses a particular part of the day to pray and receive spells. The time is usually associated with some daily event. If some event prevents a character from praying at the proper time, he must do so as soon as possible. If the character does not stop to pray for spells at the first opportunity, he must wait until the next day to prepare spells.
The time required to prepare spells is the same as it is for a wizard (1 hour)
As with arcane spells, at the time of preparation any spells cast within the previous 8 hours count against the number of spells that can be prepared.
SRP Arcane Casting said:
Must have 8 hours of restful calm before preparing.
To prepare any spell, a wizard must have enough peace, quiet, and comfort to allow for proper concentration. The wizard’s surroundings need not be luxurious, but they must be free from overt distractions. Exposure to inclement weather prevents the necessary concentration, as does any injury or failed saving throw the character might experience while studying. Wizards also must have access to their spellbooks to study from and sufficient light to read them by.