Roman Numerals and Military Time

Objective 1

Key terms

Arabic Numerals

The number system used in the Western Hemisphere, related to the English system of measurement.

Military Time

Time based on a 24-hour clock.

Roman Numerals

Letter symbols used by the ancient Romans to represent numbers.

Rounding Down

Leaving the number being rounded as it currently appears; done when the digit to the right of the number is a 4 or lower digit.

Rounding Numbers

Approximating a large number to a specific place value or whole number.

Rounding Up

Increasing the value the number being rounded by 1; done when the digit to the right of the number is a 5 or higher digit.

Traditional Time

The use of a.m. and p.m. to determine 24-hour cycle on a 12-hour clock.

This chapter discusses topics that I like to refer to as the idiosyncrasies of health care math. In the health care careers, we encounter:

• Documentation using military time

• Roman numerals used in documentation

• Roman numerals used to identify laboratory testing

Objective 2

Review of roman numerals

The use of Arabic numerals is the numbering system most of us have grown up with. It consists of numbers 0 to 9. All other numbers are based on the various combinations and at what place value each digit is placed.

Roman numerals are letters, commonly written with upper-case letters but occasionally written with lower-case letters, to represent a specific number. As the letters are put together, a different number is created (Table 2-1). The use of Roman numerals as a numbering system is as old as the concept of medicine.

Table 2-1

Roman Numerals Compared with Arabic Numerals

Roman Numeral (Letter) Upper Case and Lower Case	Arabic Numeral
ss―	12
I i	1
V v	5
X x	10
L l	50
C c	100
D d	500
M m	1,000

Data from Mulholland JM: The nurse, the math, the meds: Drug calculations using dimensional analysis, St. Louis, 2007, Mosby, and Fulcher RM, Fulcher EM: Math calculations for pharmacy technicians: A worktext, St. Louis, 2007, Saunders.

MATH TRIVIA 2-1

Do you have problems remembering the Roman numerals for 50, 100, 500, and 1,000? Try this mnemonic: Lovely Cats Don’t Meow.

MATH ETIQUETTE 2-1

Arabic numerals use commas to separate periods. Roman numerals do not use commas.

MATH TRIVIA 2-2

Do you remember what a period is in math?

Answer: A period is when larger numbers are grouped by three places. The number 564,321 has two periods in it—thousands period and one period.

Why Do We Use Roman Numerals?

Many factors influence when and where Roman numerals are used. Roman numerals are a part of the apothecary system of measurement, which has been used by physicians for writing medication orders. It was common practice to use Roman numerals when writing medications in small dose increments. They were usually written in lower case with a line drawn over the numerals to prevent misinterpretation of the order. The implementation of the Joint Commission’s current guidelines, however, has led to many changes in the way physicians write medication prescriptions to reduce the potential for error. One change has been the elimination of the apothecary system for writing medication orders. Roman numerals continue to be used to identify different clotting factors found in a person’s blood.

*Example:*
…111

*Example:*
v or ··v11

HUMAN ERROR 2-1

Be very careful when interpreting medication orders written with Roman numerals or written with both Roman numerals and Arabic numerals. Many errors occur when a V, which represents a 5, is confused with a U, which represents units. (For example, ··v11 [seven] might be confused with 2 units.) This is why many facilities have discontinued the use of Roman numerals when writing medication orders.

How to Write Roman Numerals

Roman numerals have their own set of rules to ensure proper translation of these numeric symbols:

If the letter is repeated, the number of times the letter is written represents the Arabic numeral.

Example:

II = 2

Letters are never to be repeated more than three times.

PRACTICE THE SKILL 2-1

Express the following Arabic numerals as Roman numerals

1. 7 _______________________________________

2. 5 _______________________________________

3. 8 _______________________________________

4. 11 _______________________________________

5. 15 _______________________________________

6. 42 _______________________________________

7. 65 _______________________________________

8. 100 ______________________________________

9. 2006 _____________________________________

10. 75 _______________________________________

Express the following Roman numerals as Arabic numerals

11. IV _______________________________________

12. CC _______________________________________

13. XXX _____________________________________

14. XIX _______________________________________

15. MVIII _____________________________________

16. LXV _______________________________________

17. VIII _______________________________________

18. XXXII _____________________________________

19. XVI _______________________________________

20. XIX _______________________________________

Objective 3

Military time

Documentation in military time involves converting a traditional 12-hour clock into 24 hours. This eliminates the need to write a.m. or p.m. after a time entry, thereby avoiding confusion. Military time is always written with four digits. The first two digits represent the hour, and the last two digits represent the minutes. A 0 is used as a placeholder for recording time with only three digits.

*Examples:*
1:00 a.m.	0100
2:15 a.m.	0215
3:30 a.m.	0330

At 10:00 a.m., a 0 is no longer needed as a placeholder. Simply write 1000 for 10:00 a.m. This method is used until 1:00 p.m.

*Examples:*
10:15 a.m.	1015
11:45 a.m.	1145
12:20 p.m.	1220

As stated before, military time is expressed by converting a 12-hour clock to a clock that counts 24 hours. The conversion begins when the time hits 1:00 p.m., which is referred to as 1300 hours. As you can see from Figure 2-1, each hour is counted from 1300 to 2359. Midnight (12 a.m.) can be documented in two different formats: 2400 or 0000. Your facility’s policy will state which format you should use to document midnight.

Figure 2-1 Military clock. (From Brown M, Mulholland JM: Drug calculations: Process and problems for clinical practice, ed 8, St. Louis, 2008, Mosby.)

*Examples:*
2:15 p.m.	1415
3:30 p.m.	1530
7:30 p.m.	1930
11:58 p.m.	2358

Use of Military Time in Health Care

Why do health care facilities use military time in their documentation? Most health care facilities operate 24 hours a day, 7 days a week, and 365 days a year (Box 2-1). The use of military time reduces documentation errors, medication errors, and treatment errors. Facilities have used a 24-hour clock to differentiate when an order has been written for a.m. or p.m. administration. Many facilities are not open 24 hours a day but are open 12 to 15 hours a day (Box 2-2). Military time is used to identify when a patient has been seen, has been treated, or has had medication dispensed or when follow-up phone calls are made.

Box 2-1 FACILITIES OPEN 24 HOURS A DAY