Hello Shekinah.
The Time-reference Characteristic must not be left blank so the error popped up.
Solution:
The 0CALDAY can be found in the cube in the following path:
Select any key figure in the update rule -> click on it ->There would be a tab for Time Ref. You would fine 0CALDAY there. Do all your manipulations here.
You can test the correctness of your data flow by the following way.
Fill all blank fields of 0CALDAY with some date e.g. 31.12.9999 and then try to pass
To understand more pl go thru the URL's
https://help.sap.com/saphelp_nw70/helpdata/en/65/4bdab4239011d5b2e30050da4c74dc/content.htm