The timestamp format that works with TDV System APIs is the "ISO 8601" format.
Example for the ISO 8601 format timestamp: 2021-12-02T14:10:36.278Z
Implementation example: System API used here: /services/webservices/system/admin/resource/operations/designProcedureByExample
<resource:designProcedureByExample xmlns:resource="http://www.compositesw.com/services/system/admin/resource" xmlns:execute="http://www.compositesw.com/services/system/admin/execute">
<resource:path>/shared/MySQL5.5/timestamp_proc</resource:path>
<resource:inputs>
<execute:parameter>
<execute:definition>INT</execute:definition>
<execute:value>11</execute:value>
</execute:parameter>
<execute:parameter>
<execute:definition>TIMESTAMP</execute:definition>
<execute:value>2021-12-02T14:10:36.278Z</execute:value>
</execute:parameter>
</resource:inputs>
<resource:commitChanges>true</resource:commitChanges>
</resource:designProcedureByExample>
Note: For this System API, each input parameter must be encapsulated separately between the <parameter> </parameter> tags.