Both are primarily audio gimmicks, and as you can guess, one speaks the date through your speakers, and the other the time.
Unfortunately both are also somewhat out of date — saydate in particular is a decade old — and my luck with ancient audio programs is less than perfect.
aoss saydate -w
For saytime, you’ll need to make sure sox is installed, but I can’t guarantee that will work either, since my Arch version of sox didn’t like the options saytime was passing to it.
As a side note, saytime is apparently only in Russian, even if the flag options are available in English.
And other than that, all I can say is … you’ll have to hear them for yourself.