From MozillaZine Knowledge Base

Issue: In Day View and Week View column headings, the date is displayed as month/day, not in the operating system format, even though elsewhere dates are correctly displayed in the operating system format, such as day/month/year.

Versions:

• Sunbird 0.3 (11 Oct 2006)
• Lightning 0.3 (11 Oct 2006)

Background:

• Fixed in development builds as of 20 October 2006 (Bug 345643 "Short date display in dayview and weekview are not localizable").

Workarounds:

• Use month/day/year as date/time system settings on your computer so format is consistent everywhere, or
• Use a nightly build newer than 20 October 2006. (See developer builds section on Sunbird download page or Lightning download page.)