diff --git a/main.py b/main.py
index b63927a..7eccf7d 100755
--- a/main.py
+++ b/main.py
@@ -1,6 +1,6 @@
 #!/usr/bin/python3
 
-from util.str_to_datetime import datetime
+from util.str_to_datetime import str_to_datetime as datetime
 
 from model.TimeSlotContainer import time_slot_container as tsc
 from model.TimeSlot import TimeSlot
@@ -35,3 +35,7 @@ if __name__ == "__main__":
 
     elif args.command == "add":
         tsc.add_time_slot(args.name, datetime(args.start), datetime(args.end))
+
+    elif args.command == "acc":
+        d = tsc.accumulate_duration(args.query)
+        print(f"{d.seconds // 3600}:{d.seconds % 3600 // 60}")
diff --git a/model/TimeSlot.py b/model/TimeSlot.py
index d084f36..a1d4368 100644
--- a/model/TimeSlot.py
+++ b/model/TimeSlot.py
@@ -42,3 +42,8 @@ class TimeSlot():
 
     def end_now(self):
         self.end = datetime.now()
+
+    def duration(self) -> datetime.timedelta:
+        end = self.end
+        if not end: end = datetime.now()
+        return self.end - self.start
diff --git a/model/TimeSlotContainer.py b/model/TimeSlotContainer.py
index 3c1519d..84a99d1 100644
--- a/model/TimeSlotContainer.py
+++ b/model/TimeSlotContainer.py
@@ -1,4 +1,6 @@
-from datetime import date, datetime
+import re
+
+from datetime import date, datetime, timedelta
 from model.DataStore import DataStore
 from model.TimeSlot import TimeSlot
 
@@ -43,5 +45,12 @@ class TimeSlotContainer:
     def delete_time_slot(self, ts: TimeSlot):
         raise NotImplementedError
 
+    def accumulate_duration(self, query: str) -> timedelta:
+        pattern = re.compile(query)
+        return sum([ts.duration() for ts in self._ds.get_all_time_slots()
+                    if pattern.search(ts.name) ], start=timedelta(0))
 
-time_slot_container = TimeSlotContainer(DataStore("data.json"))
+try:
+    time_slot_container = TimeSlotContainer(DataStore("data.json"))
+except FileNotFoundError:
+    time_slot_container = TimeSlotContainer(DataStore("data.json", create=True))
diff --git a/util/parser.py b/util/parser.py
index 45a9a9b..b44bcc2 100644
--- a/util/parser.py
+++ b/util/parser.py
@@ -27,4 +27,8 @@ def create_parser():
     parser_end = subparsers.add_parser("end", help="Ending the current event.")
     parser_end.add_argument("-e", "--end", help="End datetime")
 
+    # Create the parser for the "acc" command
+    parser_end = subparsers.add_parser("acc", help="Accumulate the duration of events.")
+    parser_end.add_argument("query", help="The regex matching for the name of the event.")
+
     return parser
diff --git a/util/str_to_datetime.py b/util/str_to_datetime.py
index 99f277c..812ff6e 100644
--- a/util/str_to_datetime.py
+++ b/util/str_to_datetime.py
@@ -1,7 +1,7 @@
 from datetime import datetime as dt
 
 
-def datetime(s: str) -> dt:
+def str_to_datetime(s: str) -> dt:
     s = s.strip()
 
     try: