Checking for Time Input

Excel provides a number of functions that return True or False depending on the content of a cell. For instance, ISBLANK returns True if a cell is empty, ISERR returns True if a cell contains an error value, and ISTEXT returns True if a cell contains text. You may wonder if it is possible to determine if a cell contains a time.

The short answer is no, you cannot—Excel contains no function to indicate if a cell contains a time. The reason is quite simple: Times and dates in Excel are technically nothing but numbers. A date is any number in the range 1 to 2958465, which represent the dates of 1/1/1900 through 12/31/9999. If you add a decimal portion to the number, then that represents a time (0 is midnight, 0.25 is 6:00 am, 0.5 is noon, etc.).

Knowing the range of values that can be used for dates and times, along with the fact that a cell containing a time should be formatted properly to display a time, you can create a formula that will indicate if a cell contains a time:

=IF(AND(CELL("format",B2)>="D6",CELL("format",B2)<="D9"),"Time Format","Not Time Format")

This formula checks the formatting applied to cell B2. If the formatting is one of the commonly used formats for times, then it returns the text "Time Format." If a different formatting is used, then the formula returns "Not Time Format."

A different approach is to check whether the value in cell B2 is a valid time value. You can do that by using a formula such as the following:

=IF(TIMEVALUE(TEXT(B2,"hh:mm:ss"))=B2, "Time Entry", "Not a Time Entry")

The function works fine as long as cell B2 contains only a time. If the cell contains both a date and time, then the function always returns "Not a Time Entry."

To get the best of both worlds—checking formats and the value in the cell—consider making a user-defined function in VBA. The reason is simple: VBA includes the IsDate function which not only looks at the current range of the number, but also checks to see that the cell is formatted as a date. The following macro provides an example as to how you could create such a function:

Function IsTime(rng As Range) As Boolean
    Dim sValue As String
    sValue = rng.Cells(1).Text
    On Error Resume Next
    IsTime = IsDate(TimeValue(sValue))
    On Error GoTo 0
End Function

To use the function, use the following formula in a cell:

=IsTime(B2)

The function reads how the value is displayed (using the text property of the cell object) and then tries to convert it with the TIMEVALUE function. If that is a date (determined by the IsDate function) then the display is a valid time. If it is not a date, VBA generates an error, which the code is programmed to ignore.