How to Calculate a Series of 30 Minute Time Intervals in Excel

How to Create a Series of 30 Minute Time Intervals in Excel

One of my readers tracks data points at 30 minute (half-hour) periods throughout the day. He asked me for some help in streamlining this process.

AutoFill the Step-value for a Series

You can use AutoFill in Excel to create this series. Here are the steps to take:

In two adjacent cells, enter the beginning time value and the time that is 30 minutes later than the beginning time value.
Select BOTH cells and AutoFill the cells in the range that you want to “populate.”

Calculate Decimal Number that Represents 30 Minutes

You can calculate the numeric value for a half-hour (30 minute) period:

Use a Formula to subtract the Start Time from the End Time.
Format the result as a Number with 6 Decimal Places.

In this case, the result is: 0.020833 which you can use as a Constant Value in a Formula.

Keyboard Shortcut to Enter the Current Time

Ctrl + Shift + : (Colon) will “time stamp” a cell.

How Excel Stores Time

While you can Format Time in a variety of ways, Excel must be able to recognize and store Time entries as Numeric entries! This means that correctly entered times align to the right-side of the cell. Time values are stored as a “decimal part of one” day. For example, 12:00 PM (Noon) is stored as 0.50 – 50% of the day has elapsed

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