Callender

I purchased my wife a I-Pad with Retina display Wi-Fi 64 GB for Christmas, and up until now she loved it. There was an up-date that we had to load, having done so my wife lost all her callender details including all birthdays for the whole year, putting on all this information too her ages so she is not happy and now does not trust the equipment, is there anything that can be done to recover the information and stop any future removal of data?

Many thanks.