Certain seeds such as this one needs the period of dormancy in the cold.
Basically what happens in nature is that this seed is shed in late
summer and early autumn. The seed then has to have a period of dormancy
because in natural conditions if the seedling was to rise it would do
so in horrible cold conditions and most likely not survive. So what
this does is stimulate the same response. After the 60-90 days the seed
"thinks" (i use this term very loosely) "oh, I've had my 3 months of winter
I think Ill be able to germinate now"... and thus germination is stimulated

The process of placing the seeds in cold conditions is termed
"stratification"

Hope this helps
David
How-Hie Ling wrote in
:

Hi,

I am getting some Chinese Jujube seeds in a packet from a seed retailer.

The instruction for planting the seeds is to store the seeds first in a
fridge around 5C for 60 - 90 days in order to aid germination. Why?

How-Hie Ling