STRFTIME sometimes returns 0000-00-00 00:00:00

Has anyone ever experienced this? I use the command:

exten => s,n,Set(CALLED_START=${STRFTIME(|EST5EDT|%Y-%m-%d %H:%M:%S)})

and once in a while, I get 0000-00-00 00:00:00 as the output. I’m not sure what’s going on. Is this a bug with Asterisk or with my server? It’s really random.

On my asterisk-1.4.19.1 running on my LaFonera WiFi router, your STRFTIME command and it seems to work. I have mine crafted as follows if you would like to see:

Well that’s the wierd thing about it! It works for me too, but not all the time!

What gives? Can some program be corrupt on my machine?