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:
| Exit date | Pos. | Player | To club | Transfer fee |
| --- | --- | --- | --- | --- |
| 15 May 2007 | DF | Hatem Trabelsi | Al-Hilal | Released |
| 23 May 2007 | DF | Sylvain Distin | Portsmouth | Free |
| 14 June 2007 | MF | Joey Barton | Newcastle United | £5.8m |
| 4 July 2007 | GK | Nicky Weaver | Charlton Athletic | Free |
| 10 July 2007 | MF | Trevor Sinclair | Cardiff City | Free |
| 16 July 2007 | DF | Stephen Jordan | Burnley | Free |
| 31 Jan. 2008 | MF | Ousmane Dabo | Lazio | Free |
| 31 Jan. 2008 | FW | Ishmael Miller | West Brom. Albion | £.9m–£1.4m |
Question:
What is the exit date of the player who transferred to Portsmouth?
Answer:
23 May 2007