john.layt.net

Here's a quote for you from Wikipedia:
"In Muslim-majority countries the legal work week in the Middle East is typically either Saturday through Wednesday (as in Algeria and Saudi Arabia), Saturday through Thursday (as in Iran) or Sunday through Thursday (as in Egypt, Syria, United Arab Emirates).  For most Israelis, the work week begins on Sunday and ends on Thursday or Friday at noon to accommodate the Jewish Sabbath which begins Friday night."
This is something KDE hasn't handled up to now, resulting in calendar widgets that often didn't draw the weekend properly for the users locale.  Another issue was the day of religious worship was tied to the calendar system, which caused issues for users in countries that use the Gregorian calendar but whose day of worship is not Sunday (e.g. Turkey, Israel, etc).
So I've added three new settings to KLocale in 4.2 to address this:
WorkingWeekStartDay - Defults to Monday
WorkingWeekEndDay - Defaults to Friday
WeekDayOfPray - Defaults to Sunday
Those locales that don't use the defaults can now set these values up correctly, and individuals can choose to override the settings for their locale in the Region/Date KCM.  The kdelibs KDateTable widget now obeys these settings when drawing the weekend header and red-letters the day of worship, and I'm working on the kdepim widget too.
I haven't updated any of the actual i18n settings files yet, so this is a call-out to the i18n and l10n people who are better placed than I to know which locales need updating to either commit the updates themselves, or e-mail me with the required details and a definitive reference for me to confirm the details against.  I will try work through the list myself at some stage, but any help is appreciated.
Something we're thinking about for 4.3 is also showing the locales public holidays in the kdelibs calendar widget like the kdepim widget does, but there's a few things to address before that happens.  Part of this will be proper support for astronomically based calendar systems.