What Is 1640 Military Time? 4:40 PM Explained

1640 military time is 4:40 PM. The first two digits are the hour on a 24-hour clock, and the last two digits are the minutes. Because 16 is greater than 12, this is an afternoon or evening time.

Quick Conversion

Separate 1640 into 16 hours and 40 minutes. For a PM time after 1259, subtract 12 from the hour:

16 - 12 = 4

Keep the minutes unchanged. The result is 4:40 PM. The date and time zone do not change this hour conversion; they only determine where and on which date the time occurs.

How to Say 1640

In military-style speech, 1640 is commonly read as “sixteen forty.” In ordinary 24-hour usage, people may simply say “16:40.” In 12-hour notation, say “4:40 PM.”

Do not insert PM after a four-digit military time. Writing 1640 PM mixes two clock systems. Use either 1640 or 4:40 PM.

Nearby Times

• 1630 = 4:30 PM
• 1640 = 4:40 PM
• 1645 = 4:45 PM
• 1650 = 4:50 PM

These examples show the rule: for hours 13 through 23, subtract 12 from the hour and preserve the minutes.

A Practical Example

A clinic appointment listed for 1640 begins at 4:40 PM. Arriving 15 minutes early means reaching the clinic by 1625, or 4:25 PM.

When a schedule crosses midnight, attach the date. A line that only says 1640 identifies a time of day, not which occurrence of that time is intended.

Common Mistakes

• Treating 1640 as a duration of 16 hours and 40 minutes
• Subtracting 12 from the minutes instead of the hour
• Dropping a zero from the minutes when the value is below 10
• Adding AM or PM to an already unambiguous 24-hour value
• Converting the clock but forgetting that two time zones may use different dates

The digits 1640 can also be a year when they appear in historical writing. Context matters: a schedule, roster, or timestamp usually signals a time; a sentence about the seventeenth century signals a year.

The Answer

1640 military time converts to 4:40 PM. Subtract 12 from the 16-hour value, leave 40 minutes unchanged, and use PM.