By using one of the next requests you can get the full history for all employees for a given company in one go. By checking on ID, timestamp and period/date fields you can easily keep track of the latest changes.
The latest changes would appear as first (see Creation Date), also possible to check changes in the future (see Start Period and Start Year).
If you want to get information for a particular employee, search on the name of the method. As an example, for other contract methods, search for "Contract" on Employee Service.
Some of the methods are working with enumeration. For more information see Nmbrs® API enumerations.