You must apply for old age pension from TR, it will only come automatically if you have a disability assessment valid up to the age of 67. The general right to a pension is from the age of 67, but you must have had legal residence in Iceland for at least 3 years between the ages of 16 and 67 to have any right to payments. You can see the processing time for pension applications here. The Social Insurance Administration pays pensions the 1st of every month.