How to Add Hours in Open Office

Written by thomasmckinlay
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How to Add Hours in Open Office
OpenOffice has a full suite of time functions. (clock image by Elena Nabokova from

Date and time in OpenOffice are stored as numbers. Whole numbers represent dates and fractional numbers represent time. For example, six hours is stored as 0.25, representing one-fourth of a day. A number of 1.5 would represent 1 day, 12 hours. In addition, the OpenOffice function "hours(ref)" will extract the hours represented by any number and return it as an integer. The "time(h,m,s)" function will translate numbers into time values.

Skill level:


  1. 1

    Enter time values in OpenOffice cells in the spreadsheet by using colon notation. Enter 5:00 to represent 5 hours. Enter 12:10:30 to represent 12 hours, 10 minutes, 30 seconds.

    How to Add Hours in Open Office
    Enter time as hours minutes and seconds separated by colons. (digital clock image by JoLin from
  2. 2

    Add values by adding the numbers in the cells. Enter 6:00 in cell A1 and 12:10:30 in cell A2. Add them together in cell A3 with the formula =A1+A2. If the cells are formatted as time variables, the result will be 18:10:30. The same three cells, if they are formatted as numbers, would appear as 0.25, 0.50729167 and 0.75729167.

    How to Add Hours in Open Office
    Add the values representing times. (plus.... image by rachid amrous-spleen from
  3. 3

    Extract the hour portion from any cell by using the "hour(ref)" function. Continuing our example, type "=hour(A3)" into cell A4 of the spreadsheet and OpenOffice will display 18, which is the sum of the hours only. Use the functions "=minutes(ref)" and "=seconds(ref)" to extract the minutes and seconds from any time number respectively. Once the hours have been extracted, add or subtract them in the same way as any other numbers.

    How to Add Hours in Open Office
    The hour function returns only the hours portion of a time variable. (open 24 hours, neon sign image by Richard Kane from
  4. 4

    Enter the function "=time(A4,0,0)" into cell A5 of the example spreadsheet. OpenOffice will display 18:00:00 as a time value. If this cell is formatted to display a number, it will be displayed as 0.75, or three-fourths of a day.

    How to Add Hours in Open Office
    The time function returns integers back into time format. (time image by sheldon gardner from
  5. 5

    Select "Format -> Cells" from the menu and choose the Numbers tab to be sure the result is displayed as a time variable. Formatting hours values that are stored as numbers is the same as formatting regular numbers.

    How to Add Hours in Open Office
    Be sure to format the result correctly. (calculation image by lefty from

Tips and warnings

  • Once hours exceed 24, the results will be displayed in days and hours.

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