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 |
| --- | --- | --- | --- | --- | --- |
| Rangers | Walter Smith | Resigned | May 1998 | Dick Advocaat | June 1998 |
| Celtic | Wim Jansen | Resigned | May 1998 | Jozef Vengloš | June 1998 |
| Dundee United | Tommy McLean | Mutual consent | 4 September 1998 | Paul Sturrock | 5 September 1998 |
| St. Johnstone | Paul Sturrock | Resigned | 5 September 1998 | Sandy Clark | 7 September 1998 |
| Motherwell | Harri Kampman | Resigned | 15 October 1998 | Billy Davies | 15 October 1998 |
| Aberdeen | Alex Miller | Sacked | 8 December 1998 | Paul Hegarty (Caretaker) | 8 December 1998 |
Question:
When was the date of appointment for St. Johnstone's manager? 
Answer:
7 September 1998