Error code when adding tags

Whenever I try to add tags to an item, or edit the tags on an item I get this error code-any suggestions?
#0 /home/flegai1/ Zend_Db_Statement_Mysqli->_execute(Array)
#1 /home/flegai1/ Zend_Db_Statement->execute(Array)
#2 [internal function]: Zend_Db_Adapter_Abstract->query('INSERT INTO `om...', Array)
#3 /home/flegai1/ call_user_func_array(Array, Array)
#4 /home/flegai1/ Omeka_Db->__call('query', Array)
#5 /home/flegai1/ Omeka_Db->query('INSERT INTO `om...', Array)
#6 /home/flegai1/ Omeka_Db->insert('RecordsTags', Array)
#7 /home/flegai1/ Omeka_Record_AbstractRecord->save()
#8 [internal function]: Mixin_Tag->afterSave(Array)
#9 /home/flegai1/ call_user_func_array(Array, Array)
#10 /home/flegai1/ Omeka_Record_AbstractRecord->delegateToMixins('afterSave', Array, true)
#11 /home/flegai1/ Omeka_Record_AbstractRecord->runCallbacks('afterSave', Array)
#12 /home/flegai1/ Omeka_Record_AbstractRecord->save(false)
#13 /home/flegai1/ Omeka_Controller_AbstractActionController->editAction()
#14 /home/flegai1/ ItemsController->editAction()
#15 /home/flegai1/ Zend_Controller_Action->dispatch('editAction')
#16 /home/flegai1/ Zend_Controller_Dispatcher_Standard->dispatch(Object(Zend_Controller_Request_Http), Object(Zend_Controller_Response_Http))
#17 /home/flegai1/ Zend_Controller_Front->dispatch()
#18 /home/flegai1/ Zend_Application_Bootstrap_Bootstrap->run()
#19 /home/flegai1/ Zend_Application->run()
#20 /home/flegai1/ Omeka_Application->run()
#21 {main}

At the top it says:
Mysqli statement execute error : Column 'time' cannot be null

Something odd is happening between saving the item itself, and saving the tag data.

Does this happen both when creating new items, and editing existing ones to add the tag? And, does the item itself appear to be added/edited correctly (except for the tag)?

Also, what version of Omeka are you using?

This sounds very much like a bug that was fixed in Omeka 2.3 ("Assigning tags to records caused an SQL error for some newer MySQL servers"). If you're not using the most recent version I'd definitely start by upgrading.

It happens when I try to add an item and update current tags.
As for the version-I have no idea. I inherited this from another person, who left months before I was hired and left no instructions-it has been trial and error all the way.
So-how do I check to see which version I am using and how do I then update if needed? (Please keep in mind I am fairly computer illiterate) Any help is appreciated.

Okay-tried to log in as admin. I guess I am on version 2.1.4.
How do I update then?

I logged onto my host, and into MySLQ-and the most recent version I can upgrade to on there is the one that I am running.

@ patrickmj: I can edit or add an item no problem as long as I do not attempt to change or add tags. If I edit the tags after editing all other information, I lose all of the changes I have made.

The only supported fix to the problem is to upgrade.

You say you can only use Omeka 2.1.4, but I don't quite understand what's restricting you from using more recent versions. The system requirements for 2.3.1, the latest Omeka version, are very similar to those for 2.1.4.

Thanks John-Basically, I am a historian-and don't know much about technical stuff. My host only supports automatic updating up to 2.1.4 because "the upgrade itself cannot be turned into an automated upgrade without issues." I have to do it manually-and the last thing I want to happen is to lose the whole site.
I will get in touch with my company technical support and see if they can help me through the process.