what is the time that fluentd write to log file

Question

This is a record that fluentd write to my log in hdfs:

     2014-11-30 00:00:01    [email protected] 123532 221241

The first field is the time key from Fluentd, but i don't know if it is the time that the record was stored in buffer or when it was written to log file ?

Would you please help me answer that question ?

Thanks !

Edit: This is my configure :

<match access.**>
 type webhdfs
 host localhost
 port 50070
 path /sendo/access.hadoop237.sendo.vn/%Y%m%d
 username hdfs
 output_include_tag false
 field_separator TAB
 remove_prefix access
 time_format %Y-%m-%d %H:%M:%S
 output_data_type attr:browserid,login_email,login_id,login_type,productId,p_name,p_url,shopId,userId,ipClient,time,u_agent,os_info,time_client,screen_size,device_name,page_id,block_id,level_cate,cate_id,combine

 localtime

 buffer_type file
 buffer_path /mnt/ramdisk/access
 buffer_chunk_limit 4m
 buffer_queue_limit 50
 flush_interval 3s
</match>