It's not actually 2 weeks at a time (I assume meaning two in the spring and two in the fall). It is a one week shift in the fall from the last Sunday in October to the first Sunday in November.
In spring (or late winter) the shift is 3-4 weeks actually, as it is from the first week in April to the second week in March. Most months (even February in leap year) can occasionally have 5 Sundays (or 5 of any other days, depending on the calendar for that year. Therefore it could be 4 weeks earlier in a 5 Sunday year.

One of the worst cases for this is in some cities that are in the far west end of their time zone (such as Michigan cities). Those towns do not have sunrise until 800 in the dead of winter. This change will cause a shift back to nearly that same time again for a second time in the year. Not great for morning commuters who were just getting used to have sun on their drive in, as well as for kids walking to school or waiting on the corner for the school bus.