diff --git a/include/lb_reki.h b/include/lb_reki.h
index 3090d91c..4b980f19 100644
--- a/include/lb_reki.h
+++ b/include/lb_reki.h
@@ -22,6 +22,12 @@ extern "C" {
 
 #define lbRk_KYUU_DAY_START 1
 
+extern int lbRk_ToSeiyouReki(lbRTC_ymd_t* seiyo_ymd, const lbRTC_ymd_t* kyuu_ymd);
+extern int lbRk_ToKyuuReki(lbRTC_ymd_t* kyuu_ymd, const lbRTC_ymd_t* seiyo_ymd);
+extern int lbRk_VernalEquinoxDay(int year);
+extern int lbRk_AutumnalEquinoxDay(int year);
+extern void lbRk_HarvestMoonDay(lbRTC_ymd_t* harvest_moon_day, int year);
+
 #ifdef __cplusplus
 }
 #endif