1. A computer implemented method of synchronizing at least a first and a second database each containing dated records such as events, wherein the records of the first database extend across a narrow date range narrower than the date range of the records of the second database, the method comprising: performing a prior synchronization across a prior date range set using the date of the prior synchronization and the narrow date range; storing the prior date range and a history file containing information representative of the content of the databases following the prior synchronization; performing a current synchronization across a date range that combines the prior date range with a current date range set using the date of the current synchronization and the narrow date range.