diff --git a/README.md b/README.md
index 20063f0..ccd4a82 100644
--- a/README.md
+++ b/README.md
@@ -39,6 +39,11 @@ and use Emacs customization interface to set `reaper-api-key` to the
 given value. On the same page at Harvest you should be able to see the
 account id you'll need for `reaper-account-id`.
 
+Harvest supports two timer modes to track time via hours duration and via start and end time.
+Use `reaper-hours-timer-mode` to customize the timer mode.
+Default value is `t` which means hours duration is used to track time.
+Set variable to `nil` if you want to track time via start and end time.
+
 ## Usage
 
 Use `M-x reaper` to open the buffer (or whatever key sequence you've bound it to). 
diff --git a/reaper.el b/reaper.el
index 3e5fe42..f778aef 100644
--- a/reaper.el
+++ b/reaper.el
@@ -49,6 +49,12 @@
   :type 'string
   :group 'reaper)
 
+(defcustom reaper-hours-timer-mode t
+  "Defines if Harvest is configured to track time via duration.
+   Non-t value means Harvest is configured to track time via start and end time."
+  :type 'boolean
+  :group 'reaper)
+
 (defconst reaper--list-format
   [("Project" 32 nil)
    ("Task" 20 nil)
@@ -189,6 +195,8 @@
                      (cons :task (reaper-alist-get '(task name) entry))
                      (cons :is_running (reaper-alist-get '(is_running) entry))
                      (cons :hours (reaper-alist-get '(hours) entry))
+                     (cons :started_time (reaper-alist-get '(started_time) entry))
+                     (cons :ended_time (reaper-alist-get '(ended_time) entry))
                      (cons :notes (let ((notes (reaper-alist-get '(notes) entry)))
                                     (if notes (decode-coding-string notes 'utf-8) ""))))))
             ;; API returns newest entry first. Simply reverse the list.
@@ -415,9 +423,14 @@ Stops any previously running timers."
          (entry (assoc entry-id reaper-timeentries))
          ;; If the timer is running add the time since the data was fetched.
          (time (reaper--hours-to-time (reaper--hours-accounting-for-running-timer entry)))
-         (new-time (reaper--time-to-hours-calculation (read-string "New time: " time)))
+         (start-time (cdr (assoc :started_time entry)))
+         (end-time (cdr (assoc :ended_time entry)))
          (harvest-payload (make-hash-table :test 'equal)))
-    (puthash "hours" new-time harvest-payload)
+    (if reaper-hours-timer-mode
+        (puthash "hours" (reaper--time-to-hours-calculation (read-string "New time: " time)) harvest-payload)
+      (progn
+        (puthash "started_time" (read-string "New start time: " start-time) harvest-payload)
+        (puthash "ended_time" (read-string "New end time: " end-time) harvest-payload)))
     (reaper-api "PATCH" (format "time_entries/%s" entry-id) harvest-payload "Updated entry")
     (reaper-refresh)))