You will need to check the terms & conditions of your individual mortgage.
In general, mortgages are linked to the Euribor rate which currently stands at approx 1.93% for the 12 month rate. As I say, you would need to check your own T&C to establish whether your mortgage is reviewed annually or 6 monthly or whatever period.
The review date & the date that the rate actually changes can be very different. For example our mortgage was agreed in September, we completed 18th October, the new rate is applied as at 1st November with the new payment being taken 1st December.
You need to check your deeds or speak to your bank to clarify.