The wiki article on the Canada Act 1982 is incorrect. Her Majesty did not sign the Canada Act 1982 into law on the steps of the Canadian Parliament in Ottawa. Most of that Act had come into force the moment Royal Assent had been given in the name of the Queen in the British Parliament the previous month.
The general rule is that an Act of Parliament comes into force on the day of Royal Assent, unless the Act itself sets a different date - either an Act can come into force on a later set date, or it can come into force on a date approved by a subsequent Royal proclamation.
The Canada Act 1982 does not have a section dealing with the date it came into force, so that means that most of it came into force on the date of Royal Assent in the British Parliament - which the note in italics under the title and citation for the Act indicates was March 29, 1982. Immediately from that date forward, the bulk of the Canada Act 1982 was in force, meaning that the British Parliament no longer had any authority to enact any law for Canada.
However, a part of the Canada Act 1982 did not come into force on Royal Assent. Section 1 of the Canada Act 1982 provides that Schedule B to the Canada Act 1982 only came into force via the process set out in the Schedule itself. Schedule B to the Canada Act 1982 sets out another Act: the Constitution Act, 1982, which contains the Canadian Charter of Rights and Freedoms, the amending formula, and so on. Schedule B obtains its legal authority as part of the Canada Act 1982, so the Royal Assent of March 29, 1982 would apply to it as well, but it did not come into force immediately.
Section 58 of the Constitution Act, 1982 provides that the Schedule was to come into force
A Royal proclamation setting the date for bringing legislation into force is not the same as Royal Assent. That’s what the picture in the wiki article shows: Her Majesty is not giving Royal Assent to the Canada Act 1982. That was done the previous month in the U.K. Parliament, and doesn’t involve signing - it’s usually just oral confirmation that the Crown assents. What Her Majesty was doing was signing the Proclamation of the Constitution Act, 1982 into force.