Dealing with Large Numbers of Seconds

Piers has a report which runs and once it is complete he logs the start time and duration, in seconds. If A1 is the start time and B1 is the number of seconds, Piers uses the following formula to determine the ending time:

=A1+TIME(0,0,B1)

The formula works fine, unless report execution took over 32,767 seconds, which often happens. Piers wonders what formula he can use to get past this apparent Excel limitation.

First, it is important to understand that what you have discovered is, indeed, a limitation of Excel. Or, more precisely, a limitation of the TIME function. The three parameters you use in the function (representing hours, minutes, and seconds) must be integer values. That is "programming speak" for the fact that each value must be in the range of 0 to 32767. Outside that range, and you get an error.

One solution is to simply make sure that you don't use a value that is outside of this range. I like this recasting of the formula, still using the TIME function:

=A1+TIME(INT(B1/3600),0,MOD(B1,3600))

Whereas the limit in your original formula meant that you could not have a report run for much more than 9 hours (32767 seconds), this revised formula will handle durations of nearly 4 years. (If you have reports that are taking more than 4 years to run, something is probably wrong!)

Of course, you could bypass using the TIME function altogether and simply come up with your own formula to add the seconds to the value in A1. This is easier than it may seem; all you need to do is remember that time values are stored, within Excel, as fractions of a day. Since there are 86,400 seconds in each day (60 seconds * 60 minutes * 24 hours), you could use this formula:

=A1+B1/86400

Just make sure that the cell containing the formula is formatted to display times, and you'll have no problem. (Just format the cell the same way that cell A1 is formatted; you can use the Format Painter to do this.)

ExcelTips is your source for cost-effective Microsoft Excel training. This tip (9419) applies to Microsoft Excel 97, 2000, 2002, and 2003. You can find a version of this tip for the ribbon interface of Excel (Excel 2007 and later) here: Dealing with Large Numbers of Seconds.