How can I track how much time (in seconds) elapses between two events? I would like to look at the time between two different values being set in a variable (separate server call). We are looking to do something similar to the TimeToComplete Plug-in described here:
Your best bet here is going to be using a cookie. Set a cookie with the timestamp when the first event is set, then when the second event fires, call the cookie and set a variable value based on the elapsed time.
If you plan to use this as a dimension, you can either use the value in seconds, or use additional logic to put them in buckets.
If you plan to use this as a metric, you can increment an event by the number of seconds that have elapsed. Recent appMeasurement libraries allow the format s.events="event1=10".