Invalid EffectiveDate in your XML envelope.
The error refers to the EffectiveDate element in your envelope XSD. This date must be in the past to be valid, to reflect the time that your inventory was logged in your own system. It must also be in an ISO-compliant format.
February 29, 2008, 1:10:30 p.m. in Seattle should be expressed as:
The ISO standard is Greenwich Mean Time (GMT). If you are in the Pacific Time Zone, you are 8 hours off GMT (7 hours off GMT in Daylight Savings). This is indicated by the "-8:00" in the formula above. If you're in the Eastern Time Zone, you are 5 hours off GMT (4 hours off GMT in Daylight Savings).
We strongly recommend that you supply your Time Zone as well as the basic date information.