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:
| Race | Circuit | Date | Pole position | Fastest lap | Winning driver | Constructor | Tyre | Report |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Monaco Grand Prix | Monaco | 10 May | Stirling Moss | Jack Brabham | Jack Brabham | Cooper - Climax | D | Report |
| Indianapolis 500 | Indianapolis | 30 May | Johnny Thomson | Johnny Thomson | Rodger Ward | Watson - Offenhauser | F | Report |
| Dutch Grand Prix | Zandvoort | 31 May | Joakim Bonnier | Stirling Moss | Joakim Bonnier | BRM | D | Report |
| French Grand Prix | Reims | 5 July | Tony Brooks | Stirling Moss | Tony Brooks | Ferrari | D | Report |
| British Grand Prix | Aintree | 18 July | Jack Brabham | Stirling Moss Bruce McLaren | Jack Brabham | Cooper - Climax | D | Report |
| German Grand Prix | AVUS | 2 August | Tony Brooks | Tony Brooks | Tony Brooks | Ferrari | D | Report |
| Portuguese Grand Prix | Monsanto | 23 August | Stirling Moss | Stirling Moss | Stirling Moss | Cooper - Climax | D | Report |
| Italian Grand Prix | Monza | 13 September | Stirling Moss | Phil Hill | Stirling Moss | Cooper - Climax | D | Report |
| United States Grand Prix | Sebring | 12 December | Stirling Moss | Maurice Trintignant | Bruce McLaren | Cooper - Climax | D | Report |
Question:
What date was Joakim Bonnier in the pole position?
Answer:
31 May