Short answer: A wrong time in a contest log comes in two kinds. A whole-log offset means that the computer clock was wrong all the time, and every QSO is shifted by the same amount. A single mistake means that one QSO, or a few, got a wrong time because of a typing slip or a manual change. They need different repairs. Measure first, correct only with evidence, and keep the original file next to the corrected one.
Why the time in the log matters
The time of a QSO is part of the QSO line in Cabrillo, and it matters for several reasons. It decides whether the QSO falls inside the contest period. It is used when the committee compares your log with the logs of other stations, because the same QSO should have about the same time in both. It also decides the hour in which your QSO appears in the statistics, and it is the basis of off-time rules in the categories that limit the operating time. The article on QSOs outside the contest period and the one on UTC clock errors describe the consequences in detail.
Because the time is used in so many ways, a wrong time is worth correcting if it can be done honestly. And because a correction changes the data that you send, it must be done with care.
Kind 1: a whole-log offset
A whole-log offset happens when the computer clock was wrong for the entire contest, or for a part of it. The usual causes are a clock that was not synchronised, a wrong time zone or a summer-time setting, a clock that had drifted, or a computer that changed its time during the contest after reconnecting to a network. In these cases, all QSOs made while the error was present are shifted by the same amount. If the clock was seven minutes fast all the time, every QSO is seven minutes late.
Other symptoms are the first QSO being before the start of the contest, or the last one being after the end. In logs of whole hours of error, for example the wrong time zone, the pattern is unmistakable, since the entire log is shifted by an hour or more. Smaller offsets are harder to notice, because the first and the last QSOs may still be inside the period. A check against your memory or your notes shows them.
Kind 2: single mistakes
Single mistakes are different. One QSO has a time that is out of line with the QSOs before and after it. Typical causes are a time entered by hand because the logger had stopped, a QSO that was added after the contest from paper notes, a QSO edited with a wrong time, or a QSO logged twice with different times. The pattern is a QSO that jumps out of the sequence: if the log is sorted by time and the QSOs have a sequence number, the QSO is out of order.
A related case is the change of the clock during the contest: the clock was wrong, then corrected, so a part of the log has an offset and the rest has none. You will see a jump in the times at the moment of the correction, and two QSOs close together in the log may have times that go backwards or forwards by several minutes. This is a combination of the two kinds, and it needs the more careful analysis.
How to measure an offset
- Find a reference. You need a moment whose real UTC time you know. Good references are an audio recording with a time signal or a clock at the start, a note in your paper log, the first QSO of the contest if you remember that you started at the exact minute, or a time announcement from a time station heard on the radio.
- Compare with the log. Find the QSO nearest to the reference in the log and read its time. The difference is your offset at that moment.
- Take a second reference. If you can, measure again at another point in the contest. If the difference is the same, the offset is constant. If it grows, the clock was drifting.
- Look for jumps. If the difference suddenly changes, there was a clock correction at that point.
Without any reference, you cannot know the offset, and a correction would be a guess. A guess is not a correction. In that case, consider whether it is better to leave the log as it is and to tell the organisers that your clock may have been inexact, if the rules provide for this.
How to correct an offset
If you have a reliable measure of a constant offset, many loggers have a function to shift the time of all QSOs or of a selection of QSOs by a given number of hours and minutes. Use it, and apply the shift only to the QSOs affected. If the clock was corrected during the contest, divide the log in two parts at the moment of the correction, and shift only the first part. After the shift, check the first and last QSOs: they must be inside the contest period, and the sequence of the QSOs must be natural.
Work on a copy. The original log from the logger is the proof of what happened, and the corrected version is a derived file. Keep both, together with a short note about what was changed and why, as described in the article on the post-contest review routine. The note should include the size of the offset, the evidence and the QSOs affected. If a committee has a question later, this note is your answer.
How to correct a single mistake
For a single QSO with a wrong time, look for the evidence of the real time: the neighbouring QSOs in the log, the notes, the audio and, in a multi-operator station, the logs of the other computers. If the QSO belongs between two others, a time between theirs is a reasonable choice, but only if the QSO really happened there. If you cannot determine the time, think about whether the QSO should stay in the log at all. The honest rule is the same as for other corrections: repair what you know.
The article on merging multi-op logs explains another source of time problems: computers of the same station with clocks that differ from one another, so the merged log has QSOs out of order. In that case, the correction is the offset between the computers, not a repair of single QSOs.
A small example
Imagine that you remember starting the contest exactly at the first minute, and that the first QSO in your log is timed six minutes later, with no gap in your notes. A second check, an audio file recorded at noon the next day with a time announcement, shows the same six minutes. The offset is constant, and the repair is a shift of the whole log by six minutes earlier. Now imagine instead that one QSO in the middle is timed forty minutes after its neighbours, and nothing else is shifted. That is a single mistake, and shifting the whole log would make everything else wrong.
What the statistics show
The statistics of your log can help you notice time problems. If the QSOs by hour show a rate in an hour when you were asleep, or an empty hour when you were operating, the time may be wrong. The report in Contest Analyzer gives QSOs by hour and band, rates, breaks and off time, and the other statistics such as countries, continents, CQ and ITU zones, WPX prefixes, distance, beam heading and callsign length and structure, with comparison with your own logs from earlier years. It also checks every callsign and every zone against official license databases and several independent reference sources and shows only the few QSOs worth a second look. You can edit calls or zones in the report and download a corrected Cabrillo. The times in your file are used as they are, so the correction of the time is something you decide and do. The tool works with Cabrillo from N1MM Logger+, DXLog and Win-Test and supports 22 contests, as shown on the contests page. Dupes are not errors.
Prevent the next one
- Synchronise the computer clock automatically, and check it against a reliable source before the contest.
- Write the exact start time of the recording and of the contest in your notes.
- Look at the clock in the logger from time to time during the contest, especially after a restart or a network change.
- Disable automatic changes of the time zone and the summer time on the contest computer.
- In a multi-op station, use the same time source on all computers.
Related reading
- Wrong PC clock or UTC errors in a contest log
- Recording audio in a contest to check doubtful QSOs
- Cabrillo QSO lines explained
The bottom line
First decide whether the time error is a whole-log offset or a single mistake. Measure an offset against a reliable reference, correct only what you can support with evidence and keep the original log next to the corrected one. Then fix the cause so that the next contest has a clean clock.
FAQ
How do I know that my whole log is shifted?
Compare a QSO whose real time you know with the log. If the difference is the same at several points, it is an offset.
Can I shift the whole log if I do not know the offset?
No. Without a reference, a shift is a guess. Read the rules and consider telling the organisers.
Where do I make the correction?
In the logger, on a copy, and then export a new Cabrillo. Keep the original file.
What if the clock was corrected in the middle of the contest?
Divide the log at that moment and correct only the part affected.
Does the time of a QSO affect the score?
It can, because QSOs outside the contest period are not valid and some categories limit operating time.
