From Tardis Wiki, the free Doctor Who reference

An anniversary was a date on which a prior event was commemorated. A type of anniversary was a wedding anniversary. (TV: The Power of Three)

The people of Calbaron III held an anniversary every year to commemorate the Twelfth Doctor overthrowing Emperor Vimlox. (COMIC: Planet of the Diners)

Behind the scenes[[edit]]

Main article: List of anniversary specials

Since its inception on 23 November 1963, the Doctor Who franchise has seen growth and celebrated various anniversaries, and over the years seen birth to an extensive host of other products and projects, all of which have been able to celebrate anniversaries of their own across the decades.