They come July, October, January and April. I typically get mine around the 10th or so (one more month yay). Every year your GST cheques are reviewed when you do your income tax. So the one you got in April may be a different amount then the one you will get in July, but for the rest of the year it will be the same amount.
PS is it cheque in Canada and check in the States?? We know how Canadians like to add the letter "u" to words (favourite, colour, etc).