Date module is missing but it's exisit I have installed Date module since i made drupal installation, i built many date fields but Suddenly this message show up when i go to my content type's manage field page "Inactive fields are not shown unless their providing modules are enabled.  

The following fields are not enabled:(here my date field and tell me date module is not enabled)"   

When open modules page can't find date module but other sub modules exist like (date tools, date views ....)  

I tried to recopy the date module and nothing change, date module still lost.

All my date fields disabled please help, thanks.
Check the permissions and owners of the date module folder inside your sites/all/modules it should be same as others...

Check drupal watchdog logs for more information on errors....