<div class="raw-html-embed"> The WEEKNUM function is one of the <a href="../../docs/userguides/spreadsheet_editor/InsertFunction.aspx#datetime" onclick="onhyperlinkclick(this)">date and time functions</a>. It used to return the number of the week the specified date falls within the year.

 <h5 class="pt8">Syntax</h5>
 WEEKNUM(serial_number, [return_type])
 The WEEKNUM function has the following arguments:
 <table style="width: 40%">
 <tbody>
 <tr>
 <th style="background-color: #f4f4f4" width="150ch">Argument</th>
 <th style="background-color: #f4f4f4">Description</th>
 </tr>
 <tr>
 <td>serial_number</td>
 <td>A number representing the date within the week, entered using the <a href="../../functions/Date.aspx" onclick="onhyperlinkclick(this)">DATE</a> function or other date and time function.</td>
 </tr>
 <tr>
 <td>return_type</td>
 <td>A numeric value used to determine on which day the week begins. The possible values are listed in the table below.</td>
 </tr>
 </tbody>
 </table>
 The return_type argument can be one of the following:
 <table style="width: 40%">
 <tbody>
 <tr>
 <th style="background-color: #f4f4f4">Numeric value</th>
 <th style="background-color: #f4f4f4">Week begins on</th>
 <th style="background-color: #f4f4f4">System</th>
 </tr>
 <tr>
 <td>1 or omitted</td>
 <td>Sunday</td>
 <td>1</td>
 </tr>
 <tr>
 <td>2</td>
 <td>Monday</td>
 <td>1</td>
 </tr>
 <tr>
 <td>11</td>
 <td>Monday</td>
 <td>1</td>
 </tr>
 <tr>
 <td>12</td>
 <td>Tuesday</td>
 <td>1</td>
 </tr>
 <tr>
 <td>13</td>
 <td>Wednesday</td>
 <td>1</td>
 </tr>
 <tr>
 <td>14</td>
 <td>Thursday</td>
 <td>1</td>
 </tr>
 <tr>
 <td>15</td>
 <td>Friday</td>
 <td>1</td>
 </tr>
 <tr>
 <td>16</td>
 <td>Saturday</td>
 <td>1</td>
 </tr>
 <tr>
 <td>17</td>
 <td>Sunday</td>
 <td>1</td>
 </tr>
 <tr>
 <td>21</td>
 <td>Monday</td>
 <td>2</td>
 </tr>
 </tbody>
 </table>

 <h5 class="pt8">Notes</h5>
 When return_type is set to 1-17, System 1 is used. This means that the first week in a year is the week that contains January 1.
 When return_type is set to 21, System 2 is used. This means that the first week in a year is the week that contains the first Thursday of the year. System 2 is commonly used in Europe according to the ISO 8601 standard.
 <a href="../../docs/userguides/spreadsheet_editor/InsertFunction.aspx#howtoapplyfunctions_block" onclick="onhyperlinkclick(this)">How to apply</a> the WEEKNUM function.

 <h5 class="pt8">Examples</h5>
 The figure below displays the result returned by the WEEKNUM function.
 <img alt="WEEKNUM Function" src="https://static-helpcenter.teamlab.info/weeknum_bfab955857.png"></div>

WEEKNUM Function

Docs

Argument	Description
*serial_number*	A number representing the date within the week, entered using the DATE function or other date and time function.
*return_type*	A numeric value used to determine on which day the week begins. The possible values are listed in the table below.

Numeric value	Week begins on	System
*1 or omitted*	Sunday	1
2	Monday	1
11	Monday	1
12	Tuesday	1
13	Wednesday	1
14	Thursday	1
15	Friday	1
16	Saturday	1
17	Sunday	1
21	Monday	2

WEEKNUM Function

Syntax

Notes

Examples

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