I'm trying to get the call duration in seconds using ESL, but it looks like the channel variables are not being set correctly.

In CHANNEL_HANGUP events, I see the following variables:

I would expect to generate the duration of the call by subtracting Caller-Channel-Answered-Time from Caller-Channel-Hangup-Time, but the hangup time is 0.  The actual call in this case was 45 seconds long.

What can I do use Freeswitch events to compute call duration?

Thanks!