What is 1800 in military time?
1800 is 6:00 PM on the 12-hour clock, and 18:00 on the civilian 24-hour clock. It is spoken aloud as “eighteen hundred hours” — never “6 o'clock”, and never with a colon in the written form.
The hour is over 12, so subtract 12: 18 − 12 = 6, and the time is PM.
Written down it is four digits with no separator and no AM or PM: 1800. The first two digits are the hour, the last two are the minutes, and the minutes are ordinary minutes — 1845 would be 6:45 PM.
Where 1800 sits in the day
1800 is 18 hours into the day and 6 hours from the next midnight. In the watch system it falls in the last dog watch, the evening changeover. Second shifts start, evening meals are served, and civilian schedules using 24-hour time — flights, trains, ferries — are dense through here.
The hours either side
Three hours in each direction, since the value you are checking is usually next to the one you actually need.
Everything else on the 24-hour clock
The full chart lists every hour and half hour from 0000 to 2330 and prints on one page — that link jumps straight to the 1800 row. For a value that is not on a half hour, the military time converter takes anything you type in either direction, including 6:00 PM and 1800.
If what actually tripped you up was midnight versus noon rather than this hour, the 12 AM vs 12 PM explainer covers why the 12-hour clock cannot settle that question on its own.