This property specifies the beginning of the validity of the Offering. A time-zone should be specified. For a time in GMT/UTC, simply add a "Z" following the time: 2008-05-30T09:30:10Z. Alternatively, you can specify an offset from the UTC time by adding a positive or negative time following the time: 2008-05-30T09:30:10-09:00 or 2008-05-30T09:30:10+09:00.