The AHS Blog

Journal Volume 35 Issue 1

Clock confusion – think about it!

This post was written by John Laycock

Why do the numbers of 1 to 12 on a clock dial have to be multiplied by 5 to allow one to work out the time?

If there are 24 hours in a day then the daily time continuum is 0 to 24. Why then do mechanical clocks split this continuum into two 12 hour segments? If the continuum has to be split surely it would make more sense to split between day and night with the daylight spanning 6am to 6pm and then night from our 6pm to 6am!

Why is noon 12pm? It is neither am nor pm - simply because we have chosen to reset the continuum at 12! Is midnight 12am? Some digital clocks will show the 60 minutes after midnight as 12.xx whilst others will show the time as 00.xx!

Several attempts have been made to design an unambiguous dial using a 24 hour clock. The modern dial below is a good example.

24-hour clock dial
24-hour clock dial ©Roly Williams

The most important element is the hour (long hand) with the minutes as secondary (short hand). The dial is numbered with the hours from 0 to 23, as time will be read as hour plus minute and thus 24 will never be appropriate. The shorter hand points to an inner annulus numbered 0 to 55 in steps of 5 to avoid the necessity to perform the mental x5 operation to calculate the minutes or seconds.

Why has this relatively simple and unambiguous display of time not been universally adopted? We still do not think 24 hours we think morning and afternoon.

What about the time warp that occurs when reading minutes? With the minute hand in the right half of the clock face it is usual in the English language to interpret time as 'past the hour' but when the hand moves to the left half of the clock face we usually switch dimension to 'to the next hour' e.g. twenty past six, twenty to seven.

Are we using the clock to display past time or future time? Past time is historical and cannot be used again, future time is at our disposal and should be used to best advantage. Thus the clock face should logically portray future time and not past time.

Taking into account the discussion above making the case for the 24 hour dial, should the numbering system be completely reversed. The dial should display the hours descending clockwise from 23 to 0 and similarly the minutes descending clockwise from 55 to 0 in steps of 5.

Will it happen – NO. We have two much time invested in the past!

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