Overview:
Cannot drag a Call to another date or time in My Schedule, because the following error occurs:
Call2_vod__c: bad field names on insert/update call: Call_Datetime_vod__c.
Root Cause:
The Call_Datetime_vod__c Field Level Security (FLS) is missing on the Call2_vod__c object.
Solution:
In order to resolve the error, add FLS to the Call_Datetime_vod__c field on the Call2_vod__c object.
Related Documentation:
CRM Help Documentation: N/A