Hi ​@stasvb ,  Are you experiencing this with a specific endpoint, or does it occur with all the endpoints in the MeasurementsForObjectHandling.svc?
If possible, could you also share your API request here? That would be very helpful in identifying any clues.

Hi, we've tried two services:
/MeasurementsForObjectHandling.svc/EquipmentObjectMeasGroupSet(TestPntSeq=xxx,ParameterCode='yyy')

and

/TechPortalMeasurementHandling.svc/AllMeasurementParamSet(DummyTrue='TRUE')/ParametersPreviousArray?$select=Contract,MchCode,ParameterCode,TestPntSeq,TestPointId,MeterId,PrevPrelRecExists,MeterFlipValue,ParameterWithUoM,LatestValidRecordValue,RegistrationDate,Objgrants,luname,keyref&$expand=MeasurementParamRef($select=MeterIdRequired,MeasurementParamType,Objgrants,luname,keyref),TestPointRef($select=Description,Objgrants,luname,keyref)&$skip=0&$top=25&odata-debug=json"

both returned time in the same format but different values, depending on X-Ifs-Time-Zone-Aware-Request value. 

Hope that helps.

This is due to legacy. Before we had time zone support all datetimes were returned as persisted in the database, unfortunately the 'Z' was added to them, which indicates UTC time zone. 

When introducing time zones this was discovered, but we deemed it too risky to change. So without the X-Ifs-Time-Zone-Aware-Request header set to true the server will return the Timestamp as persisted and with it will return it in UTC. The format is always the same .