A problem has been identified in which sftp fails when using newly created DDBJ accounts
All services have been restored. System shut down at 13:40 on September 5 due to a power outage.

I would like to know the date when the data was submitted.

In general, you can find accept date in JOURNAL line of REFERENCE 1 on DDBJ flat file.
Please note that some old data do not have the description of accept date.