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:
Thalayanai Pookal
Table title:
Airing History
Table:
<table id='hittask' contenteditable='False'>
<tr> <th colspan=1 rowspan=1 > Airing Date </th><th colspan=1 rowspan=1 > Days </th><th colspan=1 rowspan=1 > Time (IST) </th><th colspan=1 rowspan=1 > Episodes </th></tr>
<tr> <td colspan=1 rowspan=1 > 23 May 2016 - 13 October 2017 </td><td class="highlighted"  colspan=1 rowspan=3 > Mon-Fri </td><td colspan=1 rowspan=1 > 21:00 </td><td colspan=1 rowspan=1 > 1-365 </td></tr>
<tr> <td class="highlighted"  colspan=1 rowspan=1 > 16 October 2017 – 20 April 2018 </td><td class="highlighted"  colspan=1 rowspan=1 > 22:00 </td><td colspan=1 rowspan=1 > 366-499 </td></tr>
<tr> <td class="highlighted"  colspan=1 rowspan=1 > 23 April 2018 – 29 June 2018 </td><td class="highlighted"  colspan=1 rowspan=1 > 22:30 </td><td class="highlighted"  colspan=1 rowspan=1 > 500-549 </td></tr>
</table>
Question:
What days did the Thalayanai Pookal show shift from in October 16th, 2017 and on April 23, 2008?
Answer:
On 16 October 2017, the Thalayanai Pookal show shifted from Monday to Friday at 22:00 (IST). On 23 April 2018, the show shifted again to air Monday to Friday at 22:30 (IST) for 549 Episodes.