The weather can play tricks on us all, especially the plants. We had a really hot spell earlier in the year and then a cooler spell and then it went warm again. This probably tricked your trees into thinking we had a winter and it was spring again. Unfortunately they probably won't bear any fruit from the blossom at this late stage, but hey a pretty display for your garden.

You shouldn't allow newly planted trees to bear fruit in their first season as their strength needs to go into making a good root system. (Very difficult rule to keep!)
My damson has produced a solitary flower this week too - we have had a very strange year weather-wise. I'm a bit worried that trees that flower now are actually producing flowers that should be saved until next year, but there isn't much we can do about it. If they do set any fruit, harden your heart and remove it.