Please read the following table in HTML format from a webpage and then answer the question in detail according to the table. Each table cell is defined by a <td> and a </td> tag. Each table row starts with a <tr> and ends with a </tr> tag. 'rowspan=m' and 'colspan=n' represents a cell spaning over 'm' rows and 'n' columns.

Webpage title:
List of Bishops of Hildesheim
Table title:
Bishops of Hildesheim till 1235
Table:
<table id='hittask' contenteditable='False'>
<tr> <th colspan=1 rowspan=1 > Name </th><th colspan=1 rowspan=1 > From </th><th colspan=1 rowspan=1 > To </th><th colspan=1 rowspan=1 > - </th><th colspan=1 rowspan=1 > Remarks </th></tr>
<tr> <td colspan=1 rowspan=1 > Gunthar </td><td colspan=1 rowspan=1 > 815 </td><td colspan=1 rowspan=1 > 834 </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > Rembert </td><td colspan=1 rowspan=1 > 834 </td><td colspan=1 rowspan=1 > 835 </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > Ebbo </td><td colspan=1 rowspan=1 > 835 </td><td colspan=1 rowspan=1 > 847 </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 > Archbishop of Reims 816–835 </td></tr>
<tr> <td class="highlighted"  colspan=1 rowspan=1 > Altfrid </td><td colspan=1 rowspan=1 > 847 </td><td colspan=1 rowspan=1 > 874 </td><td colspan=1 rowspan=1 > - </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > Ludolf </td><td colspan=1 rowspan=1 > 874 </td><td colspan=1 rowspan=1 > 874 </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > Marquard </td><td colspan=1 rowspan=1 > 874 </td><td colspan=1 rowspan=1 > 880 </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > Wigbert </td><td colspan=1 rowspan=1 > 880 </td><td colspan=1 rowspan=1 > 908 </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > Waldbert </td><td colspan=1 rowspan=1 > 908 </td><td colspan=1 rowspan=1 > 919 </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > Sehard </td><td colspan=1 rowspan=1 > 919 </td><td colspan=1 rowspan=1 > 928 </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > Diethard </td><td colspan=1 rowspan=1 > 928 </td><td colspan=1 rowspan=1 > 954 </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > Otwin </td><td colspan=1 rowspan=1 > 954 </td><td colspan=1 rowspan=1 > 984 </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > Osdag </td><td colspan=1 rowspan=1 > 985 </td><td colspan=1 rowspan=1 > 989 </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > Gerdag </td><td colspan=1 rowspan=1 > 990 </td><td colspan=1 rowspan=1 > 992 </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > Bernward </td><td colspan=1 rowspan=1 > 993 </td><td colspan=1 rowspan=1 > 1022 </td><td colspan=1 rowspan=1 > - </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > Godehard </td><td colspan=1 rowspan=1 > 1022 </td><td colspan=1 rowspan=1 > 1038 </td><td colspan=1 rowspan=1 > Hildesheim-Bernward-Dom-Hildesia.JPG </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > Thietmar </td><td colspan=1 rowspan=1 > 1038 </td><td colspan=1 rowspan=1 > 1044 </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > Azelin </td><td colspan=1 rowspan=1 > 1044 </td><td colspan=1 rowspan=1 > 1054 </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > Hezilo </td><td colspan=1 rowspan=1 > 1054 </td><td colspan=1 rowspan=1 > 1079 </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > Udo of Gleichen-Rheinhausen </td><td colspan=1 rowspan=1 > 1079 </td><td colspan=1 rowspan=1 > 1114 </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > Bruning </td><td colspan=1 rowspan=1 > 1115 </td><td colspan=1 rowspan=1 > 1119 </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 > canonically irregular, not consecrated but imperially invested </td></tr>
<tr> <td colspan=1 rowspan=1 > Berthold I of Alvensleben </td><td colspan=1 rowspan=1 > 1119 </td><td colspan=1 rowspan=1 > 1130 </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > Bernard I </td><td colspan=1 rowspan=1 > 1130 </td><td colspan=1 rowspan=1 > 1153 </td><td colspan=1 rowspan=1 > - </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > Bruno </td><td colspan=1 rowspan=1 > 1153 </td><td colspan=1 rowspan=1 > 1161 </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > Herrmann of Wennerde </td><td colspan=1 rowspan=1 > 1162 </td><td colspan=1 rowspan=1 > 1170 </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > Adelog of Dorstadt </td><td colspan=1 rowspan=1 > 1171 </td><td colspan=1 rowspan=1 > 1190 </td><td colspan=1 rowspan=1 > - </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > Berno </td><td colspan=1 rowspan=1 > 1190 </td><td colspan=1 rowspan=1 > 1194 </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > Conrad I of Querfurt </td><td colspan=1 rowspan=1 > 1194 </td><td colspan=1 rowspan=1 > 1199 </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 > Prince-Bishop of Würzburg 1198–1202 </td></tr>
<tr> <td colspan=1 rowspan=1 > Heribert of Dahlem </td><td colspan=1 rowspan=1 > 1199 </td><td colspan=1 rowspan=1 > 1216 </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > Siegfried I of Lichtenberg </td><td colspan=1 rowspan=1 > 1216 </td><td colspan=1 rowspan=1 > 1221 </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > Conrad II of Reisenberg </td><td colspan=1 rowspan=1 > 1221 </td><td colspan=1 rowspan=1 > 1246 </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 >  </td></tr>
</table>
Question:
When was Altfrid the Bishop of Hildesheim?
Answer:
Altfrid was the Bishop of Hildesheim from 847 to 874.