Decoding Office Build Numbers

Open the About dialog box in any Office program.  Near the top, you'll find the build number of the program you're using.

If you are using Office 2003, you'll probably see something like 11.5608.5606. 
If you are using Office 12, you might see something like 12.0.3417.1005. 
In earlier versions, you'll see something similar.

While these numbers may look like unintelligible garbage, in reality they can be
used to tell interesting information about the version of Office you're using.


In Office 2003, the "11" that precedes the build number is simply to denote that
Office 2003 was version 11 of Office.  Similarly, the 12 in Office "12"
means... well, you get it.  Office XP was version 10, Office 2000 was
version 9, Office 97 was version 8.  You get the idea.

The most interesting thing to watch for is the first 4-digit number you
encounter.  In the examples above, 5608 and 3417.  These are what we
refer to as the "build number."  Every few days during the development
cycle, we compile all of the code in Office and turn it into a
"build": essentially an installable version of all the work everyone's
done up until that point.  Eventually, a build becomes "final" and that is
the one that ends up on CDs and in the store.

The 4-digit build number is actually an encoded date which allows you tell when
a build was born.  The algorithm works like this:

  • Take the year in which a project started.  For Office "12", that
    was 2003.
  • Call January of that year "Month 1."
  • The first two digits of the build number are the number of months since
    "Month 1."
  • The last two digits are the day of that month.

So, if you have build 3417, you would do the following math: "Month 1" was
January 2003.  "Month 13" was January 2004.  "Month 25" was January
2005.  Therefore, "Month 34" would be October 2005.

3417 = October 17, 2005, which was the date on which Office 12 build 3417

For Office 2003 and XP both, "Month 1" was January 2000.  So, the final
build of Office 2003, 5608, was made on August 8, 2003.

If you look at Office 2003 build numbers, you will see two four-digit
numbers, separated by a period.  The first of the two numbers represents
the build number for the program you're using (such as Outlook.)  The
second of the two numbers represents the build number for the core Office shared
library (called MSO), which is shared by all programs.

The Office 12 dialog boxes actually show the application and MSO build
numbers separately--they're both even labeled so that it's easy to tell them
apart.  The Office 12-style build numbers (12.0.3417.1005) reveal another internal artifact
of the way we do builds--something we call "dot builds."

Sometimes it's necessary to have two kinds of builds going on at once within
the Office team.  Recently, our build lab has been making both "Beta 1"
builds and "Beta 2" builds.  In order to ship a stable Beta 1, we have
slowed the rate of code changes dramatically and concentrated on just crucial
bug fixes.  At the same time, we need a place to check in all of the other
work people are doing for Beta 2--but we can't have
those changes coming in and wrecking the stability of Beta 1 at the last minute.

The solution?  The build lab makes two kinds of builds at once.  A
specific build number is chosen, and that build "becomes" Beta 1.  In this
case, 3417.  That doesn't mean that Beta 1 is done however.  As bug
fixes are checked in, we make new versions of the 3417 build, each one with an
increasing number as a suffix, separated by a period.  (A so-called "dot"
build.)  So there would be a 3417.1, 3417.2, 3417.3, and so on until Beta 1
is ready to ship.  Subtract 1000 from the second 4-digit number in the
About box to find the "dot build" number.  In the above example, 3417.1005 is the 5th "dot" build of our Beta 1 branch.

At the same time, the build lab continues to churn out Beta 2 builds on the
normal daily schedule: 3423, 3425, etc.  So, internally, we can tell which
build is which kind by the number it has.

Last point: once a product ships, the rules for build numbers become even
more complicated and different.  So, if you have Service Pack 2 for Office
2003, you might see a nonsensical number like 6552 or something.  Don't
worry about it, it's not tied directly to a date in the same way anymore.

Armed with this knowledge, you're ready to amaze the world with your secret
ability to decode Office build numbers.