Problem with bag file

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hii, I wrote a bagfile . when i do rosbag info i do get the topic list but the duration is zero sec.The start and end time are same. Here is the info listed

path:        record.bag
version:     2.0
**duration:    0.0s**
start:       Jan 01 1970 05:53:37.58 (1417.58)
end:         Jan 01 1970 05:53:37.58 (1417.58)
size:        3.8 GB
messages:    20883
compression: none [1887/1887 chunks]
types:       geometry_msgs/PoseStamped [d3812c3cbc69362b77dc0b19b345f8f5]
             sensor_msgs/PointCloud2   [1158d486dd51d683ce2f1be655c3c181]
topics:      /gps_pose                          7125 msgs    : geometry_msgs/PoseStamped
             /lidar_2d                          3028 msgs    : sensor_msgs/PointCloud2  
             /lidar_3d                          1886 msgs    : sensor_msgs/PointCloud2  
             /lidar_four_plane_scanner_layer1   2211 msgs    : sensor_msgs/PointCloud2  
             /lidar_four_plane_scanner_layer2   2211 msgs    : sensor_msgs/PointCloud2  
             /lidar_four_plane_scanner_layer3   2211 msgs    : sensor_msgs/PointCloud2  
             /lidar_four_plane_scanner_layer4   2211 msgs    : sensor_msgs/PointCloud2

I wrote the rosbag file using rosbag class . Why is this error can anyone help me out.