Time clocks, also known as punch clocks, do not use a typical 12-hour day with 60 minutes per hour. Instead, to determine the time you clocked in and out, these machines use a 24-hour clock with each hour broken down into hundredths instead of into minutes. Once you learn how to look at both the hours and minutes on the read out, you can easily convert punch clock time into standard time.

Things You Will Need
  • Time clock punch card with times on it

  • Calculator

  • Pencil

  • Paper

Write down the first time on the time card. This should have been your first clock in for the week, and there will be a letter next to the time denoting the day of the week. The time card time will be written as a decimal. It will have two digits for the hours followed by a decimal, then two digits to the right of the decimal for the minutes. Use the example of 19.20.

Write the first two digits (to the left of the decimal) on a sheet of paper. If this number is larger than 12, put it into your calculator. A number between 13 and 24 will denote that that time was in the afternoon. Follow the next step to determine the hour of the first time on the time clock card. For the example, you will write down 19, and follow the next step because 19 is larger than 12.

Subtract 12 from the first two digits of the time. Press the "-" key in your calculator and then put in 12 and enter. This will be the afternoon hour you started work. After you take 12 away from this number, you will have the p.m. time. If the number is less than 12, do nothing except write the number with a.m. beside it. This means that your time was in the morning hours. Take 12 away from the 19 used in the example, and you will have 7 p.m. for the hours.

Write down the two digits to the right of the decimal. This represents the percentage of the hour at which you clocked in. Converting this to minutes is not difficult. In the example, those two digits were 0.20.

Input the two digits with the decimal into your calculator. For instance, you will key in 0.20 if you follow the example.

Press the "x" key in order to multiply this decimal. Then, put in 60 and enter. You will be multiplying the decimal times 60 to get your final answer in minutes. For the example, that will be 0.20 X 60 = 12. This means that you clocked in 12 minutes after the hour.

Put your answer from Step 3 together with your answer from Step 6, and you will get the hours and minutes at which you first clocked in. For the example, the 19.20 on the card becomes 7:12 p.m.

Determine the number of hours and minutes you worked in a day by subtracting the first number that day, your clock-in time, from the second number on the card, your clock-out time. For instance, if your first time card time is 19.20 and your second is 23.25, put 23.25 - 19.20 = into your calculator, and you will get 4.05.

Convert your answer from Step 8 into hours and minutes by following Steps 4 through 7. You do not have to convert the first two digits to morning or afternoon because this number is the total number of hours you worked that day and not the actual time.


Remember that the number to the right of the decimal is the portion of the hour at which you clocked in; it is not the actual time in minutes. You need to convert both the hours and the minutes of your time.