Timers in SDP

Timers in SDP

I'm hoping someone can explain the timers in SDP...I may be overthinking this.
 
I'm trying to generate summary reports (details of each incident or SR) on things like:
First Response Time
Time from Created to Closed
Time from Created to Resolved
Time from Created to Assigned
Details of assigned technicians for a ticket with individual times for each tech.
Summary of all assigned techs for a ticket with individual and cumulative worklog.
 
I've already seen some really nice queries by Murali, but I really need to know where timers are placed, what triggers them.
 
For example:
 
What is the formula for response time?  Time Created to Time Closed - Time On Hold = Total time ticket was opened (how do custom statuses affect timers)?
 
Time Created to Time Resolved = Time to resolution (does this ignore time-on-hold?)
 
I'll ask about work log in a separate thread.
 
Thanks,
Adam

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