Thanks Raghu !!
As you told it is displaying the current (ePoch) time i.e calculating the time from 1970.
We want to display the time between ticket open date i.e (casd.cr.open_date) till current timestamp.
We have used the below formula:
PdmSeconds(PdmDownTime('Gold','Mon - Fri { 10:10 am - 6:10 pm }',casd.cr.open_date,PDMToday()))
Kindly suggest.