I had an experiment with this, and it's horribly complicated at the network level because the network traffic is encrypted in the application and the application has its code obfuscated.
I'm considering trying a hack, one that would flick the setting to "my contacts" long enough that it'd reload the conversation and fetch the time, then flick it back. But, that'd need considerable testing.
http://forum.xda-developers.com/showpost.php?p=54553885&postcount=57
My thoughts: