In amateur radio, we keep logs of our radio contacts as a part of our station records, and to enable sending of QSL cards via the postal mail or through an online service. We log time and date using the UTC time standard. We call it “Coordinated Universal Time” in English, but everyone around the world, regardless of language, uses the French abbreviation, “UTC.”
UTC logkeeping uses 24-hour military time. In this article, I will introduce military time and how to write it and speak it. Then I will show how I took the local clock and converted it to UTC for logging, while the clock showed local AM/PM time.
How to print and say Military Time
Midnight is the start of a new day. It is called “midnight,” “12:00 AM,” and “0000” (spoken as, “zero hundred hours”).
Military time is always printed with four figures with no colon [:] — 0000, 0100, 0230, 0304, 2359.
In this chart, please note that the first two digits are the hour. The second two digits are the minute. Always speak one “Zero” for the 00 hour.
Always speak the leading “Zero” in the minutes from 01 through 09. For 0009, say: “Zero” [Hours], “Zero Nine” [Minutes]. Do not say the words in the square brackets.
Strictly speaking, the military does not use 2400 for the midnight at the end of the day. The minute after 2359 is 0000 (Zero Hundred Hours) the next day.
From 1:00 PM through 11:00 PM, just add 12 hours to go from 1:00 to 1300, and from 11:00 to 2300.
| Local Time, AM & PM | Local Time (Military) | Spoken As |
|---|---|---|
| 12:00 AM | 0000 | Zero Hundred Hours |
| 12:09 AM | 0009 | Zero Zero Nine |
| 12:30 AM | 0030 | Zero Thirty |
| 1:00 AM | 0100 | Zero One Hundred Hours |
| 1:15 AM | 0115 | Zero One Fifteen |
| 2:00 AM | 0200 | Zero Two Hundred Hours |
| ... | ... | ... |
| 9:59 AM | 0959 | Zero Nine Fifty-Nine |
| 10:00 AM | 1000 | Ten Hundred Hours |
| 10:30 AM | 1030 | Ten Thirty |
| ... | ... | ... |
| 9:00 PM | 2100 | Twenty-One Hundred Hours |
| 10:00 PM | 2200 | Twenty-Two Hundred Hours |
| 11:00 PM | 2300 | Twenty-Three Hundred Hours |
Converting Local AM/PM Time to UTC
- To convert local time to UTC, you can use a digital clock set to read UTC in AM/PM time and use the military time chart. Here in Arizona, set the clock to seven hours ahead. If your clock can be set to read 24-hour format, all the better. Just set it seven hours ahead of local time.
Or you can use a regular clock and set it to correct local time. Use the following conversion to add seven hours to get UTC:
- For AM times:(AM Local MST) + 7 = (UTC)
- For PM times:(PM Local MST) + 7 + 12 = (UTC).
| Local Time MST | UTC |
|---|---|
| 12:00 AM or 0000 | 0700 |
| 1:00 AM or 0100 | 0800 |
| 11:00 AM or 1100 | 1800 |
| 12:00 PM or 1200 | 1900 |
| 4:59 PM or 1659 | 2359 |
| Tomorrow’s Date UTC | Tomorrow’s Date UTC |
| 5:00 PM or 1700 | 0000 |
| 6:00 PM or 1800 | 0100 |
Handling Logs With One Date Column
Logbooks rarely have separate date columns for the start and end of a QSO. This can make log entries a bit confusing, as can QSOs with more than two participants. Here are my solutions to these issues.
Given the format of an amateur radio logbook with one Date column and two Time columns, I will log today’s date (local) before 5 PM when I start a QSO and enter the UTC start time according to the samples in the table below.
The date entered is the starting date for the QSO. The ending time is assumed to be the same date. If my QSO goes past 5 PM local, I will enter the ending time as 2400, 2500, 2600 UTC, still under today’s date. This is illustrated in the sample log entry below.
The Date and Time columns are UTC 24-hour time, but the comments are local time on January 15, 2024. I started a QSO at 4:50 PM and another station joined us at 5:19 PM. I ended the conversation with both stations at 6:05 PM on January 15, local time, but entered them in the log on the two days, UTC, involved.
That, folks, is how I handled the situation with no ending-date column!
| Date | Start Time | RST | Freq | Mode | End Time | Comments |
|---|---|---|---|---|---|---|
| 1/15/24 | 2350 | 579 | 7032 | CW | 2505 | 4:50 – 6:05 PM |
| 1/16 | 0019 | 599 | “ | “ | 0105 | 5:19 – 6:05 PM |