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In Dataloader.io set regular dates to be MM/dd/yyyy and System Dates to be MM/dd/yyyy"T"HH:mm:ss.000"GMT+10:00" or if your dates are in dd/MM/yyyy then set the format to be dd/dd/yyyy"T"HH:mm:ss.000"GMT+10:00"
For reference, Date Formats in SOQL https://developer.salesforce.com/docs/atlas.en-us.soql_sosl.meta/soql_sosl/sforce_api_calls_soql_select_dateformats.htm
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