By default Date Time Field control will not show the week number on selecting the date / time. But SharePoint have hidden gem on displaying the week number, for this we no need to go for third party options.

This can be achieved by updating some settings from the Regional Settings page.

To update that settings to the specific web site,


Output



The same settings can be achieve through below Server Object Model code,
  1. using (SPSite site = new SPSite("http://sharepointsite"))
  2. {
  3. using (SPWeb web = site.OpenWeb())
  4. {
  5. // Get the Regional Settings for the web
  6. SPRegionalSettings regSettings = web.RegionalSettings;
  7. regSettings.ShowWeeks = true; //Enable the Show Weeks option
  8. web.Update();
  9. }
  10. }