diff --git a/draft/overlay/rtc.txt b/draft/overlay/rtc.md
similarity index 89%
rename from draft/overlay/rtc.txt
rename to draft/overlay/rtc.md
index a480375..66f18a2 100644
--- a/draft/overlay/rtc.txt
+++ b/draft/overlay/rtc.md
@@ -41,4 +41,4 @@ timers and alarms, etc. Equipped with PCF8523 RTC, it works great with the Raspb
 kernel support.
 
 This RTC will keep the time for about 5 years. The PCF8523 is simple and inexpensive but not a high 
-precision device. It may lose or gain a second or two per day.
\ No newline at end of file
+precision device. It may lose or gain a second or two per day.