col. 2, ln 10-27: According to one aspect of the present invention, a portable calendar system includes a wireless transceiver interface receiving a first calendar entry from a transmitting calendar system complementary to the portable calendar system, the first calendar entry identifying a first location, a first wireless receiver interface receiving location data and determining a current location of the portable calendar system, a mapping database storing geographic coordinate data and travel time information between identified locations, and an agent generating a second calendar entry input by a user and identifying a second location, the agent identifying one of the first and second calendar entries as a next appointment entry and calculating an estimated travel time for the next appointment entry in response to the determined current location, the location of the next appointment entry, and the corresponding stored travel time information. The portable calendar system maintains calendar entries in accordance with the calendar entries in the transmitting calendar system. Hence, the portable calendar system is updated with any changes generated in the transmitting calendar system, and determines the estimated travel time for the next appointment entry in the updated portable calendar system. Changes in the portable calendar system are also transmitted via the first transceiver interface for updating the transmitting calendar system, ensuring consistency between the transmitting calendar system and the portable calendar system. col. 3, ln 3-34: Still another aspect of the present invention provides a personal calendar system comprising an office calendar system having a first interface receiving primary user calendar information from a transceiver, a second interface receiving secondary user calendar information, and a first agent generating the office calendar in response to the primary user calendar information and the secondary user calendar information and outputting office calendar information representing selected portions of the office calendar to the first interface, the personal calendar system also including a portable calendar system having a first wireless transceiver interface receiving the office calendar information, a second wireless receiver interface receiving location data, and a second agent generating a personal calendar in the portable calendar system in response to the received office calendar information and the location data, the second agent outputting the secondary user calendar information including changes in the personal calendar relative to the received office calendar information. The personal calendar system ensures that the office calendar system and the portable calendar system remain synchronized by exchanging updated information related to the personal calendar. Hence, the personal calendar system enables updating by either a user of the office calendar system or a user of the portable calendar system. The secondary user calendar information output from the second agent of the portable calendar system may also include arbitration information between conflicting entries in the office calendar system and the portable calendar system, ensuring avoidance of conflicts between the office calendar system and the portable calendar system. col. 9, ln 36-55: If the message received from the portable is not a download command, the agent 16a checks in step 90 whether the received message is a schedule change request for a new calendar entry. If the received message is a schedule change request, the agent 16a updates the main calendar 30a in step 92 to include the new calendar entry input by the user. User-input entries from the portable 12 take priority over calendar entries stored in the calendar memory 30a since the calendar memory 30a is synchronized with the calendar entries stored in the calendar memory 30b. Specifically, the two-way communication between the agents 16a and 16b via the respective paging transceivers 40a and 40b synchronizes the calendar entries stored in the calendar memory 30a with the calendar entries stored in the calendar memory 30b, enabling a user entering a schedule change in the portable calendar system 12 to be aware of any prior conflicting entries in the office calendar memory 30a. Hence, no confirmation request is sent to the portable before updating the calendar in step 92. If desired, however, a request for confirmation of the schedule change may be added, if desired.