SayUnixTime() — Says the specified time in a custom format
Speaks the specified time according to the specified time zone and format. The arguments are:
unixtime
The time, in seconds, since January 1, 1970. May be negative. Defaults to now.
timezone
The time zone. See /usr/share/zoneinfo/ for a list. Defaults to the machine default.
format
The format in which the time is to be spoken. See voicemail.conf for a list of formats.
Defaults to "ABdY 'digits/at'
IMp".
exten => 123,1,SayUnixTime(,,IMp)