A specification of the limits of a time intervalhttp://dublincore.org/documents/dcmi-period/

The W3C profile of the ISO8601 standard for dates and times [W3C-DTF] is generally useful for identifying time instants but does not provide an explicit mechanism for indicating a time interval.
This document defines DCMI Period, an encoding scheme which uses a simple model to specify the limits of a time interval, and describes a method for encoding DCMI Period as a text string using the DCSV syntax [DCSV]. DCMI Period has been designed to be similar to DCMI Box [BOX] used for identifying a place, and thus allows consistent encoding of spatio-temporal information in the DCMES element Coverage, as well as consistency between Coverage and Date. The components of DCMI Period re-use the W3C-DTF syntax where possible.
DCMI Period indicates a single time interval. If an indication of a time instant is required, then W3C-DTF [W3C-DTF] is available. For multiple disjoint intervals, repeated instances of DCMI Period may be used. DCMI Period is unsuited for identification of recurring and periodic time intervals.
Examples
The Great Depression:
name=The Great Depression; start=1929; end=1939;
Perth International Arts Festival, 2000:
name=Perth International Arts Festival, 2000; start=2000-01-26; end=2000-02-20;
1999 AFL Grand Final [AFL is an obscure Australian ball game]:
start=1999-09-25T14:20+10:00; end=1999-09-25T16:40+10:00; scheme=W3C-DTF;
The Phanerozoic Eon:
start=Cambrian period; scheme=Geological timescale; name=Phanerozoic Eon;