Answer:
The default duration of checkpointing is 3600 seconds i.e. 1 hour. So, in every 1 hour Secondary NameNode performs checkpointing. If you want to change the default duration of checkpointing, you need to change the need to add this property in the hdfs-site.xml :
<property>
    <name>dfs.namenode.checkpoint.period</name>
    <value>4800</value>
    <description>
      Number of seconds between two periodic checkpoints
    </description>
</property>