UTC Time Reporting

AIM ¶ 4-2-12 — UTC Time Reporting

AIM 4-2-12 explains UTC (Zulu) time use, conversion from US time zones, the 24-hour clock, and how ATC reports time checks to the nearest quarter minute.

In Plain English

The FAA uses Coordinated Universal Time (UTC) — also called Zulu — for all operations. Whenever you mean local time on the radio, you must say "local" or the time zone (e.g., "Pacific") so there's no ambiguity.

To convert Standard Time to UTC, add the following hours:

Eastern: +5
Central: +6
Mountain: +7
Pacific: +8
Alaska: +9
Hawaii: +10

For Daylight Saving Time, subtract 1 hour from those values.

Time is given on the 24-hour clock: first two digits are the hour, last two are the minutes (e.g., 0920 = "zero niner two zero"). On the radio, you can state just the minutes when context is clear.

When a station gives you the current time for a time check, it's reported to the nearest quarter minute:

Less than 8 seconds past a quarter — round down
8 seconds or more — round up

So 0929:05 is "zero niner two niner," while 0929:10 becomes "zero niner two niner and one-quarter." This precision matters for IFR clearance void times, flight plans, and timed approaches.

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AIM Source Text

FAA AIM ¶ 4-2-12

FAA uses Coordinated Universal Time (UTC) for all operations. The word “local” or the time zone equivalent must be used to denote local when local time is given during radio and telephone communications. The term “Zulu” may be used to denote UTC. To convert from Standard Time to Coordinated Universal Time: TBL 4-2-3 Standard Time to Coordinated Universal Time A reference may be made to local daylight or standard time utilizing the 24-hour clock system. The hour is indicated by the first two figures and the minutes by the last two figures. Time may be stated in minutes only (two figures) in radiotelephone communications when no misunderstanding is likely to occur. Current time in use at a station is stated in the nearest quarter minute in order that pilots may use this information for time checks. Fractions of a quarter minute less than 8 seconds are stated as the preceding quarter minute; fractions of a quarter minute of 8 seconds or more are stated as the succeeding quarter minute.

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Oral Exam Questions a DPE Might Ask

Q1What time standard does the FAA use, and how do you indicate local time on the radio?

Per AIM 4-2-12, the FAA uses Coordinated Universal Time (UTC), which may be called "Zulu." When using local time on radio or telephone, you must say "local" or name the time zone (e.g., "Pacific") to avoid confusion.

Q2How do you convert Pacific Standard Time and Pacific Daylight Time to UTC?

Per AIM 4-2-12, add 8 hours to Pacific Standard Time to get UTC. For daylight time, subtract 1 hour from that conversion, so Pacific Daylight Time is UTC minus 7 (add 7 hours to PDT to get UTC).

Q3When a tower gives you a time check, how precise is it and how is it rounded?

Per AIM 4-2-12, current time is stated to the nearest quarter minute. Fractions of a quarter minute less than 8 seconds are stated as the preceding quarter minute; 8 seconds or more are stated as the succeeding quarter minute. For example, 0929:10 is reported as "zero niner two niner and one-quarter."

Related Paragraphs in Chapter 4

¶ 4-2-1

Pilot-Controller Communications

¶ 4-2-10

Radio Directions Phraseology

¶ 4-2-11

Speed Phraseology

¶ 4-2-13

NORDO Tower Procedures

¶ 4-2-14

VFR FSS Communications

¶ 4-2-2