Issue in Calculated Expression

Hi Experts,

Need your quick help!

We are currently facing issue while updating field Days spent in MDM.

This is a calculated filed and the expression is  as below

IF(IS_NULL(FIELD[FIELD[END_DATE_TIME]]),SYSTIME(0)[ ]-[ ]FIELD[FIELD[START_DATE_TIME]],FIELD[FIELD[END_DATE_TIME]]-FIELD[FIELD[START_DATE_TIME]])

Field                           Data Type

Start date Time          GM Time

End Date Time          GM Time

Days Spent               Text

As per expression if a request is having end date then Days spent is End date time - start date time else

Days spent should be systime - start date time.

But currently in MDM if a request is not having any end date time it is updating days spent value with some garbage values like -8.171, -7.161,-5.555 etc which i wrong.

If i recalculate manually from data manager by selecting a record or if i am restarting repository days spent value is getting updated correctly.

This really looks weird for me. Can some one please help me with this issue.

Please check attached file for better understanding.

Regards,

Vamsi