CZ-SK-MO 1998 Problem 4

For each date of year $1998$ , we calculate day $^{month}$ -year and determine the greatest power of $3$ that divides it. For example, for April $21$ we get $21^4 - 1998 =192483 = 3^3 \cdot 7129$ , which is divisible by $3^3$ and not by $3^4$ . Find all dates for which this power of $3$ is the greatest.