1800 or 1800 hours is 6:00 p.m. in regular or standard time.
Military Time is a time format using a 24 Hour Time system that eliminates the need for the designations "A.M." and "P.M.". It is sometimes referred to as "24 Hour Time".
The main difference between regular and military time is how hours are expressed. Regular time uses numbers 1 to 12 to identify each of the 24 hours in a day. In military time, the hours are numbered from 00 to 23. Under this system, midnight is 00, 1 a.m. is 01, 1 p.m. is 13, and so on.
See the list below for reference:
Midnight (12:00 AM) -- 0000 hrs
1:00 AM -- 0100 hrs
2:00 AM -- 0200 hrs
3:00 AM -- 0300 hrs
4:00 AM -- 0400 hrs
5:00 AM -- 0500 hrs
6:00 AM -- 0600 hrs
7:00 AM -- 0700 hrs
8:00 AM -- 0800 hrs
9:00 AM -- 0900 hrs
10:00 AM -- 1000 hrs
11:00 AM -- 1100 hrs
12:00 PM -- 1200 hrs
1:00 PM -- 1300 hrs
2:00 PM -- 1400 hrs
3:00 PM -- 1500 hrs
4:00 PM -- 1600 hrs
5:00 PM -- 1700 hrs
6:00 PM -- 1800 hrs
7:00 PM -- 1900 hrs
8:00 PM -- 2000 hrs
9:00 PM -- 2100 hrs
10:00 PM -- 2200 hrs
11:00 PM -- 2300 hrs
To learn more, visit Space Archive.
Check out 30 Time Management Tips For Work-Life Balance, shared by Forbes.