-// Note to translators: these strings need to be translated.
-// error strings
-// 'error.db' => 'database error',
-// 'error.field' => 'incorrect "{0}" data',
-// 'error.empty' => 'field "{0}" is empty',
-// 'error.not_equal' => 'field "{0}" is not equal to field "{1}"',
-// 'error.interval' => 'incorrect interval',
-// 'error.project' => 'select project',
-// 'error.activity' => 'select activity',
-// 'error.auth' => 'incorrect login or password',
-// 'error.user_exists' => 'user with this login already exists',
-// 'error.project_exists' => 'project with this name already exists',
-// 'error.activity_exists' => 'activity with this name already exists',
-// 'error.client_exists' => 'client with this name already exists',
-// 'error.no_login' => 'no user with this login',
-// 'error.upload' => 'file upload error',
-// 'error.period_locked' => 'can\\\'t complete the operation. records older than a certain number of days cannot be created or modified. team manager defines this in the "Lock interval in days" value on the "Profile" page. set it to 0 to remove locking. <br><br>uncompleted records (with 0 or empty duration) can be deleted.',
-// 'error.mail_send' => 'error sending mail',
-// 'error.no_email' => 'no email associated with this login',
-// 'error.uncompleted_exists' => 'uncompleted entry already exists. close or delete it.',
-// 'error.goto_uncompleted' => 'go to uncompleted entry.',
+// Error messages.
+// TODO: translate the following:
+// 'error.access_denied' => 'Access denied.',
+// 'error.sys' => 'System error.',
+// 'error.db' => 'Database error.',
+// 'error.field' => 'Incorrect "{0}" data.',
+// 'error.empty' => 'Field "{0}" is empty.',
+// 'error.not_equal' => 'Field "{0}" is not equal to field "{1}".',
+// 'error.interval' => 'Field "{0}" must be greater than "{1}".',
+// 'error.project' => 'Select project.',
+// 'error.task' => 'Select task.',
+// 'error.client' => 'Select client.',
+// 'error.report' => 'Select report.',
+// 'error.auth' => 'Incorrect login or password.',
+// 'error.user_exists' => 'User with this login already exists.',
+// 'error.project_exists' => 'Project with this name already exists.',
+// 'error.task_exists' => 'Task with this name already exists.',
+// 'error.client_exists' => 'Client with this name already exists.',
+// 'error.invoice_exists' => 'Invoice with this number already exists.',
+// 'error.no_invoiceable_items' => 'There are no invoiceable items.',
+// 'error.no_login' => 'No user with this login.',
+// 'error.no_teams' => 'Your database is empty. Login as admin and create a new team.',
+// 'error.upload' => 'File upload error.',
+// 'error.period_locked' => 'Can\\\'t complete the operation. Records older than a certain number of days cannot be created or modified. Team manager defines this in the "Lock interval in days" value on the "Profile" page. Set it to 0 to remove locking. <br><br>Uncompleted records (with 0 or empty duration) can be deleted.',
+// 'error.mail_send' => 'Error sending mail.',
+// 'error.no_email' => 'No email associated with this login.',
+// 'error.uncompleted_exists' => 'Uncompleted entry already exists. Close or delete it.',
+// 'error.goto_uncompleted' => 'Go to uncompleted entry.',
+// 'error.overlap' => 'Time interval overlaps with existing records.',
+// 'error.future_date' => 'Date is in future.',