| 3M | Quarter A subdivision of a year into four equal parts. |
| 6M | Half-year A subdivision of a year into two equal parts. |
| AA | Air hour Flight duration irrespective of time zones. |
| AD | Air day Flight duration irrespective of time zones. |
| CD | Calendar day (includes weekends and holidays) Period given as a number of days including weekends and holidays. |
| CW | Calendar week (7day) Period given as a number of 7day-weeks including holidays. |
| D | Day The twenty-four hour period during which the earth completes one rotation on its axis. |
| DC | Ten days period Period of 10 days. |
| F | Period of two weeks A period of time lasting fourteen days. Synonym: Fortnight. |
| H | Hour One of the twenty-four sub-divisions of a day. |
| HM | Half month A subdivision of a month into two equal parts. |
| M | Month One of twelve divisions of the year as determined by the Gregorian calendar. |
| MN | Minute A unit of time equal to 1/60 of an hour, or 60 seconds. |
| P | Four month period A period of time, measured in monthly increments, consisting of four sequential months. |
| S | Second A unit of time equal to 1/60 of a minute. |
| SD | Surface day The voyage duration irrespective of time zones. |
| SI | Indefinite An indefinite period. |
| W | Week Period of seven days. |
| WD | Workday Day on which work is usually done. |
| WW | 5 day work week Monday through Friday. |
| Y | Year The period of time as measured by the Gregorian calendar in which the earth completes a single revolution around the sun. |
| ZZZ | Mutually defined Period as per agreement. |