Step 1: Concept
Map out the calendar based on the starting day to find specific events.
Step 2: Meaning
If $1^{st}$ is Monday, then: $1^{st}$(M), $2^{nd}$(T), $3^{rd}$(W), $4^{th}$(Th), $5^{th}$(F), $6^{th}$(Sa). The first Saturday is the $6^{th}$.
Step 3: Analysis
The second Saturday will be $6 + 7 = 13^{th}$. We need the date of the fourth day *after* this Saturday.
Step 4: Conclusion
$13 + 4 = 17$. The date is the $17^{th}$.
Final Answer: (B)