JointTrajectory time_from_start resets to all zeros after publish()

edit

Ubuntu 12.04 ROS Hydro

I am publishing a JointTrajectory to Gazebo and monitoring the topic using rostopic echo. The data that I publish is different from what gets captured by rostopic echo. Somehow the "time_from_start" portion of the data gets zeroed out.

A snippet of my code is as follows

  # this is where I create and populate the JointTrajectory
  jt = make_trajectory_msg(plan=plan, secs=0.5, dt=0.2, frame_id='base_link' )
  rospy.loginfo("Publishing joint trajectory")
  while not rospy.is_shutdown():
    print jt
    gazebo_command_publisher.publish(jt)
    r.sleep()

As you can see, right before I call publish() I print the trajectory. Here is what the trajectory looks like before the publish()

header: 
  seq: 5
  stamp: 
    secs: 0
    nsecs: 0
  frame_id: base_link
joint_names: ['arm_joint_1', 'arm_joint_2', 'arm_joint_3', 'arm_joint_4', 'arm_joint_5']
points: 
  - 
    positions: [0.2792831707677692, 0.4627657000396006, -0.8622084888670658, 0.8533643604717218, 0.1568816032950613]
    velocities: [0.0, 0.0, 0.0, 0.0, 0.0]
    accelerations: [0.0, 0.0, 0.0, 0.0, 0.0]
    effort: []
    time_from_start: 
      secs: 0.7
      nsecs: 0

And here is the trajectory after it is captured by rostopic echo:

header: 
  seq: 5
  stamp: 
    secs: 0
    nsecs: 0
  frame_id: base_link
joint_names: ['arm_joint_1', 'arm_joint_2', 'arm_joint_3', 'arm_joint_4', 'arm_joint_5']
points: 
  - 
    positions: [0.2792831707677692, 0.4627657000396006, -0.8622084888670658, 0.8533643604717218, 0.1568816032950613]
    velocities: [0.0, 0.0, 0.0, 0.0, 0.0]
    accelerations: [0.0, 0.0, 0.0, 0.0, 0.0]
    effort: []
    time_from_start: 
      secs: 0
      nsecs: 0