If they were growing in my yard they would be 3rd or 4th year plants, given how slowly jujube grow for me. They are bigger than some jujube I planted from OGW in fall 2015.
But, from what I understand, jujube grow pretty quick in sunny CA, so I think these are likely much younger. They could be freshly grafted last spring, as that is what LE Cooke (a CA nursery which has since closed) claimed on their FAQ page. The rootstock itself probably started growing the year before, so depending on how you measure, it can be called 2 year old.