Calendar events disappeared for last year on iPhone

My events in the calendar disappeared for the past year. I had sync with icloud, and I checked setting to sync all events. However, simply has vanished except birthdays and holidays! I tried restore from previous version on icloud in my computer but nothing works. Actually from restoring from a previous version I don't have the most recent events (this week events) but they show up in iPad. Is there any way to recover the past year events in the calendar? And now if I sync the iPad will this week events disappear from there? Or will all events in iPad keep there despite sync? I have turned off wi-fi so I at least secure the events in iPad with recent weeks events. Any help to recover my caledar will be very usefull. Thank you