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:
| Team | Outgoing manager | Manner of departure | Date of vacancy | Replaced by | Date of appointment |
| --- | --- | --- | --- | --- | --- |
| Omonia | Giorgos Savvidis | Resigned | 4 March 2008 | Nedim Tutić | 4 March 2008 |
| Apollon | Yossi Mizrahi | Mutual consent | 11 May 2008 | Svetozar Šapurić | 23 May 2008 |
| Ethnikos | Svetozar Šapurić | Mutual consent | 23 May 2008 | Stéphane Demol | 24 May 2008 |
| Apollon | Svetozar Šapurić | Sacked | 9 September 2008 | Thomas von Heesen | 15 September 2008 |
| AEK | Nir Klinger | Sacked | 27 October 2008 | Makis Katsavakis | 28 October 2008 |
| AEP | Savvas Constantinou | Resigned | 3 November 2008 | Nir Klinger | 5 November 2008 |
| APOP | Eduard Eranosyan | Sacked | 27 November 2008 | Giorgos Polyviou | 27 November 2008 |
| AEK | Makis Katsavakis | Resigned | 2 December 2008 | Loizos Stefani | 2 December 2008 |
| Enosis | Marios Constantinou | Resigned | 7 December 2008 | Panayiotis Xiourouppas | 8 December 2008 |
| Alki | Christos Kassianos | Resigned | 17 December 2008 | Panayiotis Xiourouppas | 7 January 2009 |
| AEK | Loizos Stefani | Mutual consent | 18 December 2008 | Christos Kassianos | 18 December 2008 |
| Enosis | Panayiotis Xiourouppas | Mutual consent | 29 December 2008 | Eduard Eranosyan | 30 December 2008 |
| AEK | Christos Kassianos | Resigned | 15 January 2009 | Savvas Constantinou | 15 January 2009 |
| AEL | Andreas Michaelides | Mutual consent | 26 January 2009 | Mihai Stoichiţă | 27 January 2009 |
| Enosis | Eduard Eranosyan | Resigned | 28 January 2009 | Adamos Adamou & Antonis Kleftis | 29 January 2009 |
| Omonia | Nedim Tutić | Sacked | 16 March 2009 | Takis Lemonis | 17 March 2009 |
| APEP | Tasos Kyriacou | Sacked | 5 April 2009 | Willy Scheepers | 5 April 2009 |
| Anorthosis | Temuri Ketsbaia | Resigned | 13 April 2009 | Michalis Pamboris | 13 April 2009 |
Question:
What was the date of appointment for Christos Kassianos who belonged to AEK?
Answer:
18 December 2008