A method and apparatus for updating a local database at a mobile electronic device, from a remote database over a wireless network is provided. The local database is for storing availability data. First request data is transmitted to the remote database over the wireless network and first availability data for a first time period is subsequently received therefrom. The first availability data comprises data representative of at least a first invitee's availability during the first time period. Second request data is assembled, the second request data for requesting, from the remote database, at least the first invitee's availability during only a second time period. The second request data is transmitted to the remote database. Second availability data is subsequently receiving therefrom, the second availability data comprising data representative of at least the first invitee's availability during only the second time period. The second availability data is stored in the local database if the second availability data is indicative that at least the first invitee is available during the second time period.