The below End of Support Calendar shows all Microsoft Operating Systems end of support dates, whether they are the end of mainstream support that updates features and cosmetic changes or extended support, which ends security fixes and all Microsoft technical support other than old web pages.
Microsoft Office 2003 End of Extended Support
Includes all programs within this version of Microsoft Office, but the security problems apply in particular to software that receives information from the Internet: Outlook.
End of extended support refers to the date when Microsoft no longer provides automatic fixes, updates, or online technical assistance.
Mainstream support (non-security bug fixes and feature updates) of this version of Office ended April 14, 2009.