A temporal entity is an entity that models the period of time when a row is valid with respect to system time (or transaction time, when the transaction is recorded), business time (or valid time, when the data is valid with respect to information about the real world), or both.
To be considered valid, the fact that is being modeled is only true during a certain period of time. The two types of periods are defined in detail in this document.
A period is an interval of time that is defined by two date or time attributes in a temporal entity. A period contains a begin attribute and an end attribute. The begin attribute indicates the beginning of the period, and the end attribute indicates the end of the period. The beginning value of a period is inclusive, but the ending value of a period is exclusive. For example, if the begin attribute has a value of 01/01/1995, that date belongs in the row. Whereas, if the end attribute has a value of 03/21/1995, that date is not part of the row.
In the logical data modeling phase, you create system period attributes that model a pair of attributes that should be system-maintained values that indicate the period of time when a transaction occurs. The begin attribute contains the timestamp value for when a row is created, either by an insert operation or an update operation on an existing row. The end attribute contains the data type DATE or TIMESTAMP that specifies when the row is no longer valid.