## Allow time input at 15-min intervals only – Data Validation

### How to limit user to input time at 15-min intervals, i.e. 00:15, 00:30, 00:45, 01:00, etc.?

We talked about how to limit user to input Time in the previous post.  Let’s go one step further with Custom Data Validation, where you can put a logical formula to determine what can be input.  Only when the formula returns a TRUE result, the input is validated.

#### How?

1. Select the range of cells for Data Validation, say A2:A10 in our example.
2. Data –> Validate –> Data Validation…
3. Allow “Custom”
4. Input the formula: =MOD(MINUTE(A2),15)=0

Note: Make sure A2 is the active cell; and it is a Relative Reference (i.e. no \$ sign for A2) Optional 1) : We may give an instruction to user by input a message in the “Input Message” tab Optional 2) : We may also alert user when incorrect data is input in the “Error Alert” tab Remember to press OK when all is set.

A message box pop up (like a comment) when the cell with Data Validation is selected. A dialogue box pop up when invalid data is input. Most likely, users will follow your worksheet design to input the data in a way you need; and thus save you lot of time in cleansing the data before processing.

## So, how the formula works?

MINUTE returns only the minute of a time value, from 0 to 59.

so MINUTE(“1:00”) returns 0, MINUTE(“1:01”) returns 1, etc…

MOD returns the remainder after number is divided by divisor.

By wrapping MINUTE(A2) in MOD with a divisor of 15, i.e. =MOD(MINUTE(A2),15) returns a result from 0 to 14.

Altogether, =MOD(MINUTE(A2),15)=0 returns TRUE only when the minute of the time is either 00, 15, 30, or 45.

The following screenshot describes everything.  