Better comments.

src/main.c

@@ -319,6 +319,9 @@ static void DoReminders(void)
 /*                                                             */
 /*  DSE                                                        */
 /*                                                             */
+/*  DSE stands for "Days Since Epoch"; the Remind epoch is     */
+/*  midnight on 1990-01-01                                     */
+/*                                                             */
 /*  Given day, month, year, return DSE date in days since      */
 /*  1 January 1990.                                            */
 /*                                                             */