There are several projects/examples that read back time/weather to the caller floating around on the 'net. Most are open source so you can freely
rip them off borrow from them with attribution. If you want to learn how to add custom dialplan to a FreePBX system, you might want to start here
The actual content won’t help you directly, but the concepts for Custom Destinations will.
The community is here to provide pointers when you get stuck, not do it for you.
Also there is the speaking clock built into FreePBX feature codes. If you want to see how that is done you can search the file