Excel 2010 Bible

Chapter 12: Working with Dates and Times

257

Inconsistent date entries ................................................................................

You need to exercise caution when entering dates by using two digits for the year. When you do

so, Excel has some rules that kick in to determine which century to use. And those rules vary,

depending on the version of Excel that you use.

Two-digit years between 00 and 29 are interpreted as 21st century dates, and two-digit years

between 30 and 99 are interpreted as 20th-century dates. For example, if you enter 12/15/28,

Excel interprets your entry as December 15, 2028. But if you enter 12/15/30, Excel sees it as

December 15, 1930 because Windows uses a default boundary year of 2029. You can keep the

default as is or change it via the Windows Control Panel. From the Regional and Language Options

dialog box, click the Customize button to display the Customize Regional Options dialog box.

Select the Date tab and then specify a different year.

Figure 12.3 shows this dialog box in Windows Vista. This procedure may vary with different ver-

sions of Windows.

FIGURE 12.3

Use the Windows Control Panel to specify how Excel interprets two-digit years.

Tip
The best way to avoid any surprises is to simply enter all years using all four digits for the year. n