Printing shifts like this are not that uncommon on Canadian stamps but can be interesting as they illustrate how difficult it is to print accurately at the high speed required for stamp production.
As to value that usually depends on how great the shift is and also what the visual effect on the final stamp is. In all honesty I do not think these are worth much of a premium but sellers on eBay
sometimes have different opinions. I would suggest looking round eBay
and the other auction sites which should give you an idea as to what is on the market.
These will never be listed in catalogues as they are not constant varieties. The amount of and direction of the shift varies greatly. For the two examples you show the top one has a small shift to the left and the bottom one a small shift to the right. The "correct" stamp, as wert showed has the dates symmetrical horizontally. There is also a difference in the vertical alignment of the black print.