each subscriber requires and slotting the messages into the appropriate subscriber box. It is important that the clerk remain alert to prevent slotting messages into the wrong box. This could cause an  undelivery  situation.  The  distribution  clerk,  who handles  a  great  number  of  messages  throughout  the watch,  must  be  aware  of  high-precedence  messages  and ensure  that  they  are  reproduced  and  distributed  in  a timely manner for immediate pickup by the subscriber. The clerk must also be “up” on the message center’s current  SOP  for  handling  special  and  classified messages. To  prevent  viewing  by  unauthorized  personnel, certain   messages,   such   as   PERSONAL   FOR, AMCROSS,  and  classified  messages,  must  be  placed  in envelopes for pickup by subscribers. Classified messages are placed in two envelopes; the inner envelope is stamped with the classification and any special-handling markings, and then sealed in accordance with local instructions. The outer envelope is marked with the addressee, originator, and DTG of the message, and then sealed. After reproducing and distributing a message, the distribution clerk places the original copy into a box for filing by the file clerk. When a message is reproduced from the sole copy of a broadcast message, the original copy or a filler must be returned to the broadcast file. If two-ply paper is used on the circuit, the top copy may be used as the master file copy and the bottom copy retained as the circuit monitor copy. COMMON MESSAGE ELEMENTS Before  covering  the  basic  format  of  military messages, we will first discuss the time system and precedence categories used in naval communications. TIME Time is one of the most important elements in communications.  Messages  are  normally  identified and filed by either date-time group or Julian date, depending on the method of transmission. Date-Time Group The  date-time  group  (DTG)  is  assigned  for identification  and  file  purposes  only.  The  DTG  consists of six digits. The first two digits represent the date, the second two digits represent the hour, and the third two digits  represent  the  minutes.  For  example,  221327Z AUG 96 means the 22nd day of August plus the time in Greenwich mean time (GMT). The dates from the first to the ninth of the month are preceded by a zero. We will talk more about the GMT system shortly. The DTG designation is followed by a zone suffix and the month and year. The month is expressed by its first three letters and the year, by the last two digits of year of origin; for example, 081050Z AUG 96. The zone suffix ZULU (Z), for Greenwich mean time, is used  as  the  universal  time  for  all  messages.  The exception  is  where  theater  or  area  commanders prescribe  the  use  of  local  time  for  local  tactical situations. Radiomen never use 2400Z and 0000Z as the DTG of a message. The correct time would be either 2359Z or 0001Z, as appropriate. GREENWICH   MEAN   TIME.—   In  naval communications,  the  date-time  group  is  computed  from a common worldwide standard. To meet the need for worldwide time standardization, the international Greenwich mean time (GMT) system was developed. The GMT system uses a 24-hour clock instead of the two 12-hour cycles used in the normal civilian world. In the GMT system, the Earth is divided into 24 zones. Zone zero lies between 7 1/2° east and 7 1/2° west of the 0° meridian. The 0° meridian passes through Greenwich, England. The time in this zone (zone zero) is called Greenwich mean time (GMT). The military more commonly refers to this as  ZULU  time.  Both names refer to the same standard. Each time zone extends through 15° of longitude. Zones located east of zone zero are numbered 1 through 12  and  are  designated  minus.  To  obtain  Greenwich mean time, you must subtract the zone number in which you are located from local time. Zones  located  west  of  zone  zero  are  also  numbered 1 through 12 but are designated plus. These zones must be added to the local zone time to obtain GMT. As we will discuss shortly, the 12th zone is divided by the 180th  meridian,  which  is  the  international  date  line. Each zone is further designated by a letter. Letters A through M (J is omitted) designate the eastern, or minus, zones. Letters N through Y designate the western, or plus, zones. The designating letter for GMT is Z (ZULU). The zone number, prefixed by a plus or minus  sign,  constitutes  the  zone  description.  Zones crossing land areas often follow boundaries, natural features, or regional demarcations to keep similar or closely related areas within the same zone. 2-19