Within the accuracy of Zogg's measurement capability, the same configuration of sunrise at the same azimuth/elevation will appear on the same date in one year.
Since the actual "calendar year" is 365.24 days (approximately) the time of day at which the precise "solstice moment" appears changes slightly, hence there is a slight lateral drift of the solar path apparent from his observation point.
For a "more nearly exact" alignment he'll have to wait four years for the "leap year adjustment" to resynchronise. For an "almost exact" alignment he'll have to wait 100 years for realignment with the leap year that's dropped out in even centuries.
For truly precise observations, he should refer to "sidereal time" rather than calendar or clock time, and probably should synchronise his observations with the atomic clocks and the international timekeepers, to keep track of the "leap second" corrections that accomodate wobble and drift in the earth's motions.