diff --git a/docs/features/extracted.rst b/docs/features/extracted.rst
index 84120a1d..0e7daad0 100644
--- a/docs/features/extracted.rst
+++ b/docs/features/extracted.rst
@@ -108,8 +108,8 @@ Name                        Units         Description
 =========================   =========     =============
 count                       SMS           Number of SMS of type ``sms_type`` that occurred during a particular ``day_segment``.
 distinctcontacts            contacts      Number of distinct contacts that are associated with a particular ``sms_type`` during a particular ``day_segment``.
-timefirstsms                hours         Number of hours between 12:00am (midnight) and the first ``SMS`` of a particular ``sms_type``.
-timelastsms                 hours         Number of hours between 12:00am (midnight) and the last ``SMS`` of a particular ``sms_type``.
+timefirstsms                minutes        Number of minutes between 12:00am (midnight) and the first ``SMS`` of a particular ``sms_type``.
+timelastsms                 minutes        Number of minutes between 12:00am (midnight) and the last ``SMS`` of a particular ``sms_type``.
 countmostfrequentcontact    SMS           Number of ``SMS`` messages from the contact with the most messages of ``sms_type`` during a ``day_segment`` throughout the whole dataset of each participant.
 =========================   =========     =============
 
diff --git a/src/features/sms/sms_base.R b/src/features/sms/sms_base.R
index fe6f4b4e..64335adb 100644
--- a/src/features/sms/sms_base.R
+++ b/src/features/sms/sms_base.R
@@ -44,8 +44,8 @@ base_sms_features <- function(sms, sms_type, day_segment, requested_features){
             feature <- switch(feature_name,
                     "count" = feature %>% summarise(!!paste("sms", sms_type, day_segment, feature_name, sep = "_") := n()),
                     "distinctcontacts" = feature %>% summarise(!!paste("sms", sms_type, day_segment, feature_name, sep = "_") := n_distinct(trace)),
-                    "timefirstsms" = feature %>% summarise(!!paste("sms", sms_type, day_segment, feature_name, sep = "_") := first(local_hour) + (first(local_minute)/60)),
-                    "timelastsms" = feature %>% summarise(!!paste("sms", sms_type, day_segment, feature_name, sep = "_") := last(local_hour) + (last(local_minute)/60)))
+                    "timefirstsms" = feature %>% summarise(!!paste("sms", sms_type, day_segment, feature_name, sep = "_") := first(local_hour) * 60 + first(local_minute)),
+                    "timelastsms" = feature %>% summarise(!!paste("sms", sms_type, day_segment, feature_name, sep = "_") := last(local_hour) * 60 + last(local_minute)))
 
             features <- merge(features, feature, by="local_date", all = TRUE)
         }