Does hydrochloric acid change in concentration over time?
First of all, check the expiry date. In general HCl solutions are secondary standards. 1 N is just a approximation. You need to standardize it every time with a primary standard such as sodium carbonate. On the other hand, constant boiling HCl is indeed a primary standard. It is not very well known, perhaps because modern analytical chemists have become lazier.

Constant-boiling hydrochloric acid
John L. Sheldon
J. Chem. Educ., 1935, 12 (8), p 377
https://pubs.acs.org/doi/abs/10.1021/ed012p377