diff --git a/src/format.cpp b/src/format.cpp
index 8f8f854b..fb295857 100644
--- a/src/format.cpp
+++ b/src/format.cpp
@@ -1,11 +1,24 @@
-#include <string>
-
 #include "format.h"
 
+#include <sstream>
+#include <string>
+
 using std::string;
 
-// TODO: Complete this helper function
+// DONE: Complete this helper function
 // INPUT: Long int measuring seconds
 // OUTPUT: HH:MM:SS
-// REMOVE: [[maybe_unused]] once you define the function
-string Format::ElapsedTime(long seconds[[maybe_unused]]) { return string(); }
\ No newline at end of file
+string Format::ElapsedTime(long seconds) {
+  long hours = seconds / 3600;
+  long minutes = (seconds % 3600) / 60;
+  long secs = seconds % 3600 % 60;
+  std::ostringstream formatted_time{};
+  string s_hours =
+      hours <= 9 ? "0" + std::to_string(hours) : std::to_string(hours);
+  string s_minutes =
+      minutes <= 9 ? "0" + std::to_string(minutes) : std::to_string(minutes);
+  string s_seconds =
+      secs <= 9 ? "0" + std::to_string(secs) : std::to_string(secs);
+  formatted_time << s_hours << ":" << s_minutes << ":" << s_seconds;
+  return formatted_time.str();
+};
\ No newline at end of file