# Is h:mm:ss time format clear without a key?

I have a table of data, and two of the columns contain an amount of time. This is for an American audience; an international solution is better, but not at the expense of usability for the American audience. Said audience is fairly specific and we can assume a fair bit of contextual knowledge.

I am currently displaying the amounts of time in the h:mm:ss format (so an hour and a half, and four seconds would be 1:30:04; five minutes would be 0:05:00). The column headings clearly indicate that these are amounts of time (specifically, "Duration" and "Delay," both of which are terms we can assume the audience understands).

Therefore, I have two questions:

1. Is there any time format that is clearly superior to this one for clearly displaying amounts of time in a table?

2. Is this format clear about what it is, without anything in the column header explaining it? I could use, e.g., "Duration (hr:min:sec)" or something, but it looks ugly and I'm not sure it's any clearer.

Ultimately, we will change these formats as requested by the client, but for the initial test they want to see what we can come up with, so “just ask them” is not a valid answer. We will get feedback, and it may include critique of the time format, but we are not at that stage yet. I just want to try to ensure our first impression is clear.

• How important are the seconds? For example, is showing a duration of 5 min unacceptable for the value 0:05:07 or 0:04:58? – DaveAlger Feb 20 '15 at 21:37
• @DaveAlger They are required, yes. How important they actually are, I do not know and might discuss it with the client later, but for now the spec says to include them. – KRyan Feb 20 '15 at 21:40
• Don't show them and see if they notice. – rr1g0 Feb 21 '15 at 2:06
• It's worth asking, as it's probably the client didn't think of this when writing specs. In many cases, as you get a longer duration, precision becomes less important. When the duration is a couple minutes, seconds are significant, but become irrelevant if you're talking about several hours. A common way to do this is to display the "fuzzy" time (eg 1h 23m), but on hover, display the full detail (1h 23m 52.320s). How fuzzy it should be (10 hours 51 minutes vs about 11 hours vs half a day) is another question entirely. – gregmac Feb 21 '15 at 5:17
• @rr1g0 Not my call to deviate from spec, doubt my boss would OK it. – KRyan Feb 21 '15 at 16:42

hh:mm:ss is a fairly standard way of displaying duration. I would hazard a guess that most people have used and are familiar with a stopwatch. That's the format that's used in pretty much all stopwatches.

If you must have something else for comparison, try 5h 10m 22s if you need exact time. (display min & sec if it's under an hour, and sec only if it's under a minute).

• I would appreciate if you could back up your claims in the first paragraph; I suppose most stopwatches I’ve seen do use this format, and I suppose most people have seen one, but I wonder if the different context might confuse people. As for the second paragraph, that does look good; I’ll have to see if I can get the software to continue to sort correctly if it’s in that format (it unfortunately currently only does lexicographical sorting). – KRyan Feb 20 '15 at 21:42
• @KRyan I'm not sure how you'll be able to state absolutely that this the most common format. But a general google image search for digital stopwatches show 80+% of the pictures uses this format. google.ca/… Would like to hear more on how exactly are you using this duration and maybe that'll help determine what's the right approach. – nightning Feb 20 '15 at 21:46

## The order is clear to most users as long as there are 2 colons

Using only numbers and colons is usually less clear than using time based suffixes hour, min, sec.

Ambiguity happens when there is only a single colon. For example, 4:58 could either refer to 4 hours and 58 minutes or 4 minutes and 58 seconds.

As long as there are two colons and a time based word as the column title such as Duration or Delay then most people will properly put the largest unit of time on the left hours and the smallest unit of time on the right seconds.

## Avoid dealing with seconds unless they truly matter

From a usability standpoint I would really try to avoid dealing with seconds at all unless they are critical to the task at hand. The exact second an event is logged to a file might be critical but for most activities tracking seconds is more frustrating than rounding to the nearest minute or 5 minutes even.