SOFTWARE VERSION:
Nokia N900
Maemo 5
Version: 2.2009.51-1

EXACT STEPS LEADING TO PROBLEM: 
1. Add the Bulgarian language to the device languages using X terminal:
$ sudo gainroot
# add_remove_language add bg_BG

2. (Optional) Copy any localized .mo files to /usr/share/locale/bg/LC_MESSAGES/
or copy the default ones from /usr/share/locale/en_GB/LC_MESSAGES/
# mkdir -p /usr/share/locale/bg/LC_MESSAGES/
# cp /usr/share/local/en_GB/LC_MESSAGES/*.mo /usr/share/locale/bg/LC_MESSAGES/

3. Start the settings application and select "Language & region"
4. Set both "Device Language" and "Regional Settings" to Bulgarian.
5. Reboot the device
6. Start Calendar application. Click "New Event"

EXPECTED OUTCOME:
The New event dialog shows and new events can be added,

ACTUAL OUTCOME:
The Calendar application closes with an "Internal Error. Application 'Calendar'
closed"

REPRODUCIBILITY:
ALWAYS

EXTRA SOFTWARE INSTALLED:
This is the output of:
dpkg-query -W -f='${Package}-${Version} ${Status} ${Section}\n' | grep
installed | grep user | sed 's/install ok.*//'

3g2g-mode-selection-applet-0.4 
account-plugin-butterfly-0.8 
account-plugin-haze-0.8 
account-plugin-salut-0.8 
angrybirds-1.1.0 
catorise-0.7.4 
conky-1.6.1-0maemo5-1.1 
countdowntimer-0.5-2 
cpumem-applet-0.0.3 
decoders-support-0.3.4-1 
fennec-1.0.0 
flashlight-applet-0.3-2 
fmradio-2010.01.15 
freoffice-0.2-1 
headphoned-1.6 
hermes-0.2.2 
kmplayer-0.10.3-1 
maemo-geolocation-1.1.3-1 
maepad-1.0 
mp-fremantle-generic-pr-2.2009.51-1 
mplayer-1.0svn20091221-4 
ogg-support-1.0.5 
omweather-0.24.12 
omweather-weather-com-stations-db-0.9.12 
openssh-1:5.1p1-6.maemo5 
openssh-client-1:5.1p1-6.maemo5 
openssh-server-1:5.1p1-6.maemo5 
personal-gprs-mon-0.5-5 
purple-extra-protocols-2.6.3-6nix0 
rootsh-1.5 
sharing-service-pixelpipe-1.1.00.4 
simple-brightness-applet-1.1-1maemo0 
simple-fmtx-widget-0.3.0 
telepathy-extras-0.8 
thai-ttf-0.4.13-1 
tickstill-1.0.4 
ttf-droid-1.01-dfsg0maemo3 
tunewiki-community-1.0.4 
ukeyboard-2.1-1 
xulrunner-1.9.2.1+rc1

OTHER COMMENTS:
We were able to identify exactly what part of the localization triggers the
crash. It is related to the somehow with the definitions inside LC_TIME, which
is switched to bg_BG only if you set "Device Language" to Bulgarian. Thats why
this problem does not exist if you only set Regional settings to Bulgarian.
I think that this itself is a bug, as LC_TIME is part of the regional settings
and should be switched.
After the reboot when the LC_TIME in /etc/osso-af-init/locale is set to bg_BG
in X terminal:
#locale -k LC_TIME | grep d_fmt
d_fmt="%e.%m.%Y"

This is the definition that triggers the crash and more specificaly the %e part
of it. According to date man page:
"%e     day of month, space padded; same as %_d"
I was able to workaround this by modifying the /usr/lib/locale/locale-achive
with hex editor (I have no knowledge how to rebuild this file) found that
string and replaced it with standard %d. So after modifying the file the output
of "locale -k LC_TIME | grep d_fmt" looks like:
#locale -k LC_TIME | grep d_fmt
d_fmt="%d.%m.%Y"

If this could help - this definition also affects (crashes) Settings -> Date
and Time.

User-Agent:       Mozilla/5.0 (X11; U; Linux x86_64; en-US) AppleWebKit/532.9
(KHTML, like Gecko) Chrome/5.0.307.5 Safari/532.9