Solution 1:

I believe the way to do this is the following:

  • Go to the Insert tab in Word
  • Quick parts
  • Field
  • Select Date from the list on the left.
  • Enter your custom date format in the text box on the right (eg. MM-DD-YY)
  • Click OK

Solution 2:

In the absence of answers suggesting simpler or more general solutions for adding custom date formats, here's what I did to solve the problem:

  • Rename the .docx file to .zip and unzip the contents to a folder.
  • Open the file word\document.xml in a text editor.
  • Search for dateformat (case-insensitively). There are two hits, something like

<w:dateFormat w:val="yy"/><w:lid w:val="de-DE"/><w:storeMappedDataAs w:val="dateTime"/><w:calendar w:val="gregorian"/></w:date></w:sdtPr><w:sdtContent><w:p w:rsidR="00331636" w:rsidRDefault="00331636"><w:pPr><w:jc w:val="right"/><w:rPr><w:sz w:val="96"/><w:szCs w:val="96"/><w14:numForm w14:val="oldStyle"/></w:rPr></w:pPr><w:r><w:rPr><w:sz w:val="96"/><w:szCs w:val="96"/><w14:textOutline w14:w="9525" w14:cap="rnd" w14:cmpd="sng" w14:algn="ctr"><w14:solidFill><w14:srgbClr w14:val="000000"/></w14:solidFill><w14:prstDash w14:val="solid"/><w14:bevel/></w14:textOutline><w14:numForm w14:val="oldStyle"/></w:rPr><w:t>11</w:t></w:r></w:p></w:sdtContent></w:sdt></w:txbxContent>

  • For both hits, change the highlighted yy to yyyy and change the 11 to 2011.
  • Save the file, zip everything up again and rename the archive to .docx. Done.

Solution 3:

Well... I did the following:

Right clicked the Date field and selected Toggle Field Codes.

It was like this:

{ TIME \@ "MMMM d, y" }

the single y was giving me a two digits year like 14.

I changed it to

{ TIME \@ "MMMM d, yyyy" }

Right clicked the Date field again and selected Toggle Field Codes.

Voila. It worked!

Now I get a four digits year: 2014.