diff --git a/erpnext/projects/doctype/time_log/test_time_log.py b/erpnext/projects/doctype/time_log/test_time_log.py
index 4a312ad..d0cf6a0 100644
--- a/erpnext/projects/doctype/time_log/test_time_log.py
+++ b/erpnext/projects/doctype/time_log/test_time_log.py
@@ -16,6 +16,15 @@
 		self.assertRaises(OverlapError, ts.insert)
 
 		frappe.db.sql("delete from `tabTime Log`")
+	
+	def test_negative_hours(self):
+		frappe.db.sql("delete from `tabTime Log`")
+		test_time_log = frappe.new_doc("Time Log")
+		test_time_log.activity_type = "Communication"
+		test_time_log.from_time = "2013-01-01 11:00:00.000000"
+		test_time_log.to_time = "2013-01-01 10:00:00.000000"
+		self.assertRaises(frappe.ValidationError, test_time_log.save)
+		frappe.db.sql("delete from `tabTime Log`")
 
 test_records = frappe.get_test_records('Time Log')
 test_ignore = ["Time Log Batch", "Sales Invoice"]
diff --git a/erpnext/projects/doctype/time_log/time_log.py b/erpnext/projects/doctype/time_log/time_log.py
index eb8afc7..b925114 100644
--- a/erpnext/projects/doctype/time_log/time_log.py
+++ b/erpnext/projects/doctype/time_log/time_log.py
@@ -19,10 +19,12 @@
 		self.set_status()
 		self.validate_overlap()
 		self.calculate_total_hours()
-
+		
 	def calculate_total_hours(self):
 		from frappe.utils import time_diff_in_hours
 		self.hours = time_diff_in_hours(self.to_time, self.from_time)
+		if self.hours < 0:
+			frappe.throw(_("\'From Time\' cannot be later than \'To Time\'"))
 
 	def set_status(self):
 		self.status = {