Calculate time difference between two date time fields

Question

I have a process builder by which I am calculating the time difference between NOW() and another Case object date field.

My formula goes like this

Time_Spent__c = NOW() - Start_Time__c

However when Time_Spent__c is not getting populated correctly. I saw that all time differences are calculated in GMT. What I would like to understand is the difference comes in what value- s(seconds) or mS (milliseconds) >

I needed my value in hours, so I used the below formula

 Time_Spent__c = ((NOW() - Start_Time__c)/(1000*60*60)) - assuming the difference is coming in milliseconds. However the value is still not coming up properly. If (NOW() -Start_Time__c ) equals 5. The time spent is coming as 1.03 which is definitely not correct. Is is a problem of the time zone

Also Start_Time__c was defaulted to NOW() when the case was created.

Answer 1

Now() - SpecifiedDateTime returns the difference in miliseconds.