Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Unit | Reactor Type | Net Capacity | Gross Capacity | Construction Start | Grid Connection | Commercial Operation | Status |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Hamaoka-1 | BWR | 515 MW | 540 MW | June 10, 1971 | August 13, 1974 | March 17, 1976 | Shutdown January 30, 2009 |
| Hamaoka-2 | BWR | 806 MW | 840 MW | June 14, 1974 | May 4, 1978 | November 29, 1978 | Shutdown January 30, 2009 |
| Hamaoka-3 | BWR-5 | 1056 MW | 1100 MW | April 18, 1983 | January 20, 1987 | August 28, 1987 | Shutdown May, 2011 |
| Hamaoka-4 | BWR-5 | 1092 MW | 1137 MW | October 13, 1989 | January 27, 1993 | September 3, 1993 | Shutdown May, 2011 |
| Hamaoka-5 | ABWR | 1212 MW | 1267 MW | July 12, 2000 | April 26, 2004 | January 18, 2005 | Shutdown May, 2011 |
Question:
When was the Hamaoka-4 unit commercial operation date?
Answer:
September 3, 1993