Time clock software programs are designed to accurately and unbiasedly record employee hours and display those hours clearly and automatically for any given payroll period. There are few things more disconcerting to new time clock software users than seeing an occasional employee’s time card that appears to have a one or two minute difference between the daily hours worked and the total hours worked for the period.
The answer to this discrepancy is much like the missing dollar puzzle. Three friends check into a motel for the night and the clerk tells them the bill is $30 for a room, so they each pay the clerk $10. A few minutes later, the clerk realizes he made a mistake and overcharged the trio by $5, so he asks the bellhop to pay the three friends $5 back. The bellboy reasons that the three friends would have a hard time dividing $5 equally among themselves, so he decides to return only $3 and keep the other $2. The three friends each get $1 back, so they each paid $9 for the room, for a total of $27 for the night. Adding this to the $2 the bellboy pocketed comes to $29. So where did the other dollar go? The reason this puzzle works so well is that it seems obvious that there is a dollar missing. The reality is that the three men paid $27 ($9 each) for a room for which the clerk only charged them $25. The extra two dollars went into the dishonest bellhop’s pocket!
Likewise, when new users of time clock software discover that “minutes are missing,” they are often surprised (and sometimes skeptical) when told that it looks like minutes are missing. Like the missing dollar puzzle, the answer to missing minutes is how the numbers are calculated and displayed in decimal format. Consider an employee who works a 20-minute shift three times a day. How long does the employee work each day? “That is easy!” you confidently say, “20 minutes times 3 equals 60 minutes or one hour per day.”
Let’s look at a sample timecard report with totals displayed as decimals:
08:00 to 08:20 = 0.33
12:00 to 12:20 = 0.33
17:00 to 17:20 = 0.33
Total hours = 1.0
Since 0.33 + 0.33 + 0.33 = 0.99, where is the time lost? You see, 20 minutes in decimal format isn’t really 0.33 at all. Actually, 20/60 = 0.3333333 to infinity, but we only use 0.33 to represent a third of something when it’s actually a little more than 0.33. So adding .3333333 (to infinity) three times gives us .9999999999 to infinity. In other words, we get a number very close to 1, but not exactly 1. Even if we used really long decimals in our timecard reports, we could never represent exactly 3 twenty-minute shifts as 60 minutes. So we show 20 minutes as just 33 hours, which is fine until 3 turns of twenty minutes don’t add up to 1 full hour!
Make sure your time clock software tracks employee clocking times and performs internal calculations using minutes instead of decimals, so times always add up to the exact number of minutes the employee worked. To calculate time cards in decimal format, your time clock software must add up the total minutes worked, divide by 60, and display the total to 2 decimal places. Since employee time clock software accurately reports every minute an employee works, the missing time is a result of how the math rules you learned in grade school apply to decimal numbers.
