diff --git a/chrono/format.h b/chrono/format.h
index ae922c2..b0b09af 100644
--- a/chrono/format.h
+++ b/chrono/format.h
@@ -2,6 +2,7 @@
 #define CHRONO_FORMAT_H
 
 #include "./datetime.h"
+#include "./period.h"
 
 #include <ostream>
 
@@ -15,4 +16,9 @@ inline std::ostream &operator<<(std::ostream &out, const ChronoUtilities::TimeSp
     return out << value.toString(ChronoUtilities::TimeSpanOutputFormat::Normal, false);
 }
 
+inline std::ostream &operator<<(std::ostream &out, const ChronoUtilities::Period &value)
+{
+    return out << value.years() << " years, " << value.months() << " months, " << value.days() << " days";
+}
+
 #endif // CHRONO_FORMAT_H