The time stamp format proposed here does not include time zone and daylight saving time. So it can be ambiguous and may cause interoperability problems between different time zones.
A notion of time zone and daylight saving can be added or the current time can be calculated from UTC internally and stored as UTC time stamps in the serialized form.
Part 4, Section 3.17.4.2
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Proposed Disposition of DIS 29500 Comment IR-0044 (Modified: 2008-01-02) While we understand the comment, and agree that there is no way in SpreadsheetML to designate or differentiate between “standard time” and “daylight savings time” in those locations where time shifts are used, we do not plan to make any changes to the specification to support “daylight savings time.” SpreadsheetML assumes that all times are specified using UTC or using time zone offsets from UTC as specified by ISO 8601. If ISO 8601 is updated with a standard representation for differentiating “standard” and “daylight savings” time, we recommend that the SpreadsheetML specification be updated to match. Note that we do understand the importance of supporting ISO 8601 date and time formats (including time zones), and have added support for specification of UTC dates and times using an ISO 8601 format in response to several other comments, including AU-0017 and JP-0071. Similar Comments: CH-0010 , GR-0024 , IR-0045
