HFCC Math Lab
NAT – 08
Military Time
Military time is a concise method of expressing time used by the military, law enforcement, hospitals,
and other entities. For fields in which accuracy of time is important, a 24-hour time scale eliminates
confusion about whether a.m. or p.m. was meant. Subsequently, the use of a.m. or p.m. becomes
unnecessary. The numbers used for hours range from 00 to 23 instead of 1 to 12 used twice. Below is
a table that shows corresponding times for military times and regular times.
Regular Time
12:00 a.m.
(Midnight)
1:00 a.m.
2:00 a.m.
3:00 a.m.
4:00 a.m.
5:00 a.m.
6:00 a.m.
7:00 a.m.
8:00 a.m.
9:00 a.m.
10:00 a.m.
11:00 a.m.
Military Time
0000
0100
0200
0300
0400
0500
0600
0700
0800
0900
1000
1100
Regular Time
12:00 p.m.
(noon)
1:00 p.m.
2:00 p.m.
3:00 p.m.
4:00 p.m.
5:00 p.m.
6:00 p.m.
7:00 p.m.
8:00 p.m.
9:00 p.m.
10:00 p.m.
11:00 p.m.
Military Time
1200
1300
1400
1500
1600
1700
1800
1900
2000
2100
2200
2300
Note: In writing military time
1) There is no colon separating the hours from the minutes.
2) The first two digits refer to the hour and the second two digits refer to the minutes
3) The time is always written with 4 digits. Thus when the hour uses only 1 digit in regular
time, “0” is added at the start for military time. For example 1:00 am is written as 0100
and not 100
As far as the digits go, there is no difference in writing the minutes, the only difference lies in
writing the hours from 1 p.m. to before 1:00 a.m.
1
Revised 4/11
Conversion from one time to the other
Military to Regular Time
Decide whether the time is a.m. or p.m.
The first 2 digits represent the hour. If the number represented by those digits is less than 12
then the time is an a.m. time. If the number represented by those digits is 12 or more then the
time is a p.m. time
Continue to write as regular time.
If the digits for the hours represent a number that is greater than 12, you need to subtract 12
from the military time hour to get the regular time hour. If the digits for the hours are 00, it
refers to the first hour of the day and you use 12:**. Otherwise, use the same number for the
regular time hour omitting any initial zeros. The next two digits represents the minutes past
the hour. Both systems use minutes the same way so no conversion is needed.
Examples:
1) Convert 1543 to regular time.
• The first two digits15 gives a number that is greater than 12 so you need to
subtract: 15-12 = 3.
• Also we know that it is a p.m. time since 15 is a number that is 12 or more
Thus the regular time will be 3:43 p.m.
2) Convert 0245 to regular time
• The first two digits 02 gives a number that is not greater than12 so there is no
need to subtract
• Also we know that it is a.m. time since 02 gives a number that is less than 12
Thus the regular time will be 2:45 a.m.
3) Convert 1200 to regular time
• The first two digits12 gives a number that is not greater than 12 so there is no
need to subtract
• Also we know that it is a p.m. time since 12 is a number that is 12 or more
Thus the regular time will be 12:00 p.m.
4) Convert 0001 to regular time
• The first two digits 00 give a number that is not greater than 12, but since it is the
special case of 00, we know that the hour is 12 in regular time.
• Also we know that is a.m. time since 00 is a number that is less than 12
Thus the regular time will be 12:01 a.m.
2
Revised 4/11
Regular to Military Time
For a.m. times keep the hour the same (except for the 12 a.m. hour – instead you use 00 for the
hour).
For p.m. hour add 12 to the hour (except for the 12 p.m. hour - keep the hour as 12)
Remember that if the hour is a 1 digit number you have to add a leading zero.
Examples:
1) Convert 3:46 a.m. to military time
• This time is in the morning, so the hour stays the same and we add a leading zero
Thus the military time is 0346
2) Convert 4:15 p.m.to military time
• This time is in the afternoon so add 12 to the hour 4 to get 16
Thus the military time is 1615
3) Convert 12:42 a.m. to military time
• This time is in the morning but it is the 12 a.m. hour so instead we use 00 for the
hour.
Thus the military time is 0042
4) Convert 12:42 p.m.to military time
• Although this time is in the afternoon, it is the 12 p.m. hour so we do not add 12
to the hour.
Thus the military time is 1242
Other less common military time formats that you may encounter:
1) Sometimes military time is expressed as above but with the word hours written at the end.
Example: 1531 hours
2) When expressing time down to the second, a colon is inserted between the minutes and
seconds. Example: 1531:22 or 1531:22 hours
3) In a few instances 2400 is used for the midnight instead of 0000.
4) Science and engineering fields sometimes use colons to separate both minutes and seconds
when using military time. Example: 15:31 or 15:31:22
Exercises:
Convert the following military times to regular times:
1) 0342
2) 1223
3) 1920
4) 1624
5) 0002
6) 1128
Convert the following regular times to military times:
7) 4:42 p.m.
8) 4:15 a.m.
9) 12:21 a.m.
10) 12:21 p.m.
11) 11:31 p.m.
12) 10:21 a.m.
3
Revised 4/11
Solutions:
1) 3:42 a.m.
2) 12:23 p.m.
3) 7:20 p.m.
4) 4:24 p.m.
5) 12:02 a.m.
6) 11:28 a.m.
7) 1642
8) 0415
9) 0021
10) 1221
11) 2331
12) 1021
4
Revised 4/11