We are observing the same issue on 10.9.1 Server on a 2019 SQL DB. It was found that a hosted feature service can be updated as expected; however, the featureServer Service from the SQL DB rounds to seconds. This limitation is unexpected. Due to the limitation and data use case we have had to add in separate seconds and nanoseconds attributes to capture the data feed. It appears that this defect has been persistent with no resolution and limited reasoning. 1) NIM096852 - Query operations using the time parameter are not adequately precise in the ArcGIS REST API. 2) BUG-000082768 : For the datetime(2) and datetime data types, the Date Field does not show data in milliseconds. 3) ENH-000104683 : Enhance date fields in feature services to support millisecond resolution when adding, editing, or querying features.
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