In some embodiments, a system includes a database of trust information that internalizes security and trust relationships between a first entity and a second entity in regards to scheduling, and a central trust manager operable to determine from the database of trust information whether a trust relationship exists between a first organization and a second organization, the central trust manager also being operable to provide availability information of a user of the first organization to a second user of the second organization, the central trust manager also being operable to determine whether the second user of the second organization is granted access to requested calendar data and the central trust manager also being operable to provide the requested calendar data.